fix(notification): save smtp sender without reentering password

Preserve the saved SMTP password when connection settings are unchanged and keep it out of admin forms.

Ref: IT-1601

.dockerignore

@@ -7,3 +7,4 @@
 **/*.suo
 **/TestResults
 NuGet.Config
+docker/kubernetes/

.gitignore

@@ -480,3 +480,6 @@ $RECYCLE.BIN/
 
 # Vim temporary swap files
 *.swp
+
+# Local Docker Compose secrets and ports
+docker/environments/.env.local

AGENTS.md

@@ -0,0 +1,27 @@
+# HrynCo Notification Service Agent Rules
+
+## Git workflow
+
+- Treat `main` as the only default and integration branch for this repository.
+- Start every task branch from the latest `origin/main`.
+- Before creating a task branch, fetch the remote, switch to `main`, and fast-forward it from `origin/main`.
+- Create the task branch only after confirming that local `main` matches `origin/main`.
+- Open pull requests from the task branch into `main`.
+- Do not use `development` as the base or pull-request target for new work in this repository.
+- Do not commit, push, publish, deploy, or merge unless the repository owner explicitly requests that step.
+
+Recommended branch preparation:
+
+```text
+git fetch origin
+git switch main
+git pull --ff-only origin main
+git switch -c <task-branch>
+```
+
+## Delivery
+
+- Keep changes focused and preserve backward compatibility where practical.
+- Update the matching repository documentation when behavior, contracts, configuration, routing, or workflows change.
+- Run the solution build and relevant tests before handoff.
+- Use Conventional Commit messages with a lowercase subject and finish the commit body with `Ref: <issue-id>` when an issue exists.

Directory.Packages.props

@@ -30,13 +30,15 @@
     <PackageVersion Include="Serilog.Sinks.Seq" Version="9.0.0" />
     <!-- HrynCo shared packages -->
     <PackageVersion Include="HrynCo.Common" Version="1.0.11" />
-    <PackageVersion Include="HrynCo.RabbitMq" Version="1.0.15" />
+    <PackageVersion Include="HrynCo.RabbitMq" Version="1.0.17" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
     <PackageVersion Include="coverlet.collector" Version="6.0.4" />
     <PackageVersion Include="xunit" Version="2.9.3" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.4" />
     <PackageVersion Include="NSubstitute" Version="5.3.0" />
+    <!-- Patched test-only dependency pulled by Testcontainers. -->
+    <PackageVersion Include="SSH.NET" Version="2026.0.0" />
     <PackageVersion Include="Testcontainers.PostgreSql" Version="4.6.0" />
-    <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="9.0.5" />
+    <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="10.0.6" />
   </ItemGroup>
 </Project>

HrynCo.NotificationService.Contracts/HrynCo.NotificationService.Contracts.csproj

@@ -9,7 +9,7 @@
     <Description>RabbitMQ message contracts for HrynCo.NotificationService.</Description>
     <PackageTags>hrynco notification email rabbitmq contracts</PackageTags>
     <RepositoryType>git</RepositoryType>
-    <RepositoryUrl>https://gitea.grynco.com.ua/hrynco/hrynco-notification-service.git</RepositoryUrl>
+    <RepositoryUrl>https://gitea.hrynco.com/hrynco/hrynco-notification-service.git</RepositoryUrl>
   </PropertyGroup>
 
   <ItemGroup>

HrynCo.NotificationService.DAL.Abstract/Repositories/IEmailTemplateDefinitionRepository.cs

@@ -0,0 +1,14 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Repositories;
+
+public interface IEmailTemplateDefinitionRepository
+{
+    Task<IReadOnlyList<EmailTemplateDefinition>> GetDefinitionsAsync(string? serviceName = null, string? key = null, CancellationToken ct = default);
+    Task<EmailTemplateDefinition?> GetDefinitionAsync(string serviceName, string key, CancellationToken ct = default);
+    Task<EmailTemplateDefinition?> GetDefinitionAsync(Guid serviceId, string key, CancellationToken ct = default);
+    Task<EmailTemplateDefinition?> UpsertDefinitionAsync(EmailTemplateDefinitionPatch patch, CancellationToken ct = default);
+    Task<IReadOnlyList<EmailTemplateDefinition>> GetDefinitionsAsync(Guid serviceId, CancellationToken ct = default);
+    Task<bool> DeleteDefinitionAsync(Guid serviceId, string key, Guid revision, CancellationToken ct = default);
+    Task SaveDefinitionAsync(EmailTemplateDefinition definition, bool isNew, CancellationToken ct = default);
+}

HrynCo.NotificationService.DAL.Abstract/Repositories/IEmailTemplateRepository.cs

@@ -4,7 +4,7 @@ namespace HrynCo.NotificationService.DAL.Abstract.Repositories;
 
 public interface IEmailTemplateRepository
 {
-    Task<IReadOnlyList<EmailTemplate>> GetAllAsync(CancellationToken ct = default);
+    Task<IReadOnlyList<EmailTemplate>> GetAllAsync(string? serviceName = null, string? key = null, CancellationToken ct = default);
     Task<IReadOnlyList<EmailTemplate>> GetByServiceAsync(string serviceName, CancellationToken ct = default);
     Task<EmailTemplate?> GetAsync(string serviceName, string key, string languageCode, CancellationToken ct = default);
     Task AddAsync(EmailTemplate template, CancellationToken ct = default);

HrynCo.NotificationService.DAL.Abstract/Repositories/INotificationServiceRepository.cs

@@ -0,0 +1,13 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Repositories;
+
+public interface INotificationServiceRepository
+{
+    Task<IReadOnlyList<NotificationServiceInfo>> GetAllAsync(CancellationToken ct = default);
+    Task<NotificationServiceInfo?> GetAsync(Guid id, CancellationToken ct = default);
+    Task<NotificationServiceInfo?> GetByNameAsync(string name, CancellationToken ct = default);
+    Task<bool> DeleteAsync(Guid id, Guid revision, CancellationToken ct = default);
+    Task SaveAsync(NotificationServiceInfo service, bool isNew, CancellationToken ct = default);
+    Task RemoveLanguageAsync(Guid serviceId, Guid languageId, int expectedVersionCount, Guid expectedRevision, CancellationToken ct = default);
+}

HrynCo.NotificationService.DAL.Abstract/Templates/EmailTemplateDefinition.cs

@@ -0,0 +1,13 @@
+using HrynCo.DAL.Abstract.Entities;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class EmailTemplateDefinition : Entity
+{
+    public Guid ServiceId { get; set; }
+    public required string ServiceName { get; set; }
+    public required string Key { get; set; }
+    public Guid Revision { get; set; }
+    public IReadOnlyList<EmailTemplateVariable> Variables { get; set; } = [];
+    public IReadOnlyList<EmailTemplate> Languages { get; set; } = [];
+}

HrynCo.NotificationService.DAL.Abstract/Templates/EmailTemplateDefinitionPatch.cs

@@ -0,0 +1,11 @@
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class EmailTemplateDefinitionPatch
+{
+    public Guid ServiceId { get; init; }
+    public required string Key { get; init; }
+    public Guid? Revision { get; init; }
+    public required IReadOnlyList<EmailTemplateVariable> Variables { get; init; }
+    public required IReadOnlyList<EmailTemplate> Translations { get; init; }
+    public IReadOnlyList<string> RemoveLanguageCodes { get; init; } = [];
+}

HrynCo.NotificationService.DAL.Abstract/Templates/EmailTemplateValidation.cs

@@ -0,0 +1,76 @@
+using System.Text.Json;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public static class EmailTemplateValidation
+{
+    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
+    {
+        PropertyNameCaseInsensitive = false,
+        UnmappedMemberHandling = System.Text.Json.Serialization.JsonUnmappedMemberHandling.Disallow
+    };
+
+    public static IReadOnlyList<EmailTemplateVariable> ParseVariables(string json)
+    {
+        using var document = JsonDocument.Parse(json);
+        if (document.RootElement.ValueKind == JsonValueKind.Null)
+            throw new EmailTemplateWriteException("Variables must be a JSON array.", false);
+        if (document.RootElement.ValueKind != JsonValueKind.Array)
+            throw new JsonException("Variables must be an array.");
+        foreach (var item in document.RootElement.EnumerateArray())
+            ValidateVariableShape(item);
+        var variables = JsonSerializer.Deserialize<List<EmailTemplateVariable>>(json, JsonOptions);
+        ValidateVariables(variables);
+        return variables!;
+    }
+
+    private static void ValidateVariableShape(JsonElement item)
+    {
+        if (item.ValueKind != JsonValueKind.Object)
+            throw new JsonException("Each variable must be an object.");
+        if (!item.TryGetProperty("name", out var name) || name.ValueKind != JsonValueKind.String)
+            throw new JsonException("Every variable needs a name string.");
+        if (!item.TryGetProperty("required", out var required) || required.ValueKind is not (JsonValueKind.True or JsonValueKind.False))
+            throw new JsonException("Every variable needs a required boolean.");
+    }
+
+    public static void ValidateVariables(IReadOnlyList<EmailTemplateVariable>? variables)
+    {
+        if (variables is null)
+            throw new EmailTemplateWriteException("Variables must be a JSON array.", false);
+        if (variables.Any(v => v is null || string.IsNullOrWhiteSpace(v.Name)))
+            throw new EmailTemplateWriteException("Every variable needs a non-empty name.", false);
+        if (variables.Select(v => v.Name).Distinct(StringComparer.Ordinal).Count() != variables.Count)
+            throw new EmailTemplateWriteException("Variable names must be unique.", false);
+    }
+
+    public static bool ContractsEqual(IReadOnlyList<EmailTemplateVariable> left, IReadOnlyList<EmailTemplateVariable> right) =>
+        left.OrderBy(v => v.Name, StringComparer.Ordinal).SequenceEqual(right.OrderBy(v => v.Name, StringComparer.Ordinal));
+
+    public static void ValidateIdentity(string serviceName, string key)
+    {
+        if (string.IsNullOrWhiteSpace(serviceName) || serviceName.Length > 100)
+            throw new EmailTemplateWriteException("Service name is required and must be at most 100 characters.", false);
+        if (string.IsNullOrWhiteSpace(key) || key.Length > 100)
+            throw new EmailTemplateWriteException("Key is required and must be at most 100 characters.", false);
+    }
+
+    public static void ValidateLanguage(EmailTemplate template)
+    {
+        if (string.IsNullOrWhiteSpace(template.LanguageCode) || template.LanguageCode.Length > 10)
+            throw new EmailTemplateWriteException("Language code is required and must be at most 10 characters.", false);
+        if (string.IsNullOrWhiteSpace(template.Subject) || string.IsNullOrWhiteSpace(template.HtmlBody) || string.IsNullOrWhiteSpace(template.TextBody))
+            throw new EmailTemplateWriteException("Every language needs a subject, HTML body, and text body.", false);
+    }
+
+    public static void ValidateDefinition(EmailTemplateDefinition definition)
+    {
+        ValidateIdentity(definition.ServiceName, definition.Key);
+        ValidateVariables(definition.Variables);
+        foreach (var language in definition.Languages)
+            ValidateLanguage(language);
+        var codes = definition.Languages.Select(t => t.LanguageCode);
+        if (codes.Distinct(StringComparer.Ordinal).Count() != definition.Languages.Count)
+            throw new EmailTemplateWriteException("Language codes must be unique within a template.", false);
+    }
+}

HrynCo.NotificationService.DAL.Abstract/Templates/EmailTemplateWriteException.cs

@@ -0,0 +1,6 @@
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class EmailTemplateWriteException(string message, bool isConflict = true) : Exception(message)
+{
+    public bool IsConflict { get; } = isConflict;
+}

HrynCo.NotificationService.DAL.Abstract/Templates/NotificationServiceInfo.cs

@@ -0,0 +1,9 @@
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class NotificationServiceInfo
+{
+    public Guid Id { get; set; }
+    public required string Name { get; set; }
+    public Guid Revision { get; set; }
+    public IReadOnlyList<ServiceLanguageInfo> Languages { get; set; } = [];
+}

HrynCo.NotificationService.DAL.Abstract/Templates/ServiceLanguageInfo.cs

@@ -0,0 +1,8 @@
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class ServiceLanguageInfo
+{
+    public Guid Id { get; set; }
+    public required string Code { get; set; }
+    public int VersionCount { get; set; }
+}

HrynCo.NotificationService.DAL.EF/Configurations/EmailTemplateDefinitionEntityConfiguration.cs

@@ -0,0 +1,29 @@
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace HrynCo.NotificationService.DAL.EF.Configurations;
+
+internal sealed class EmailTemplateDefinitionEntityConfiguration : IEntityTypeConfiguration<EmailTemplateDefinitionEntity>
+{
+    public void Configure(EntityTypeBuilder<EmailTemplateDefinitionEntity> builder)
+    {
+        builder.ToTable("email_template_definitions");
+        builder.HasKey(x => x.Id);
+        builder.Property(x => x.Id).HasColumnName("id");
+        builder.Property(x => x.ServiceId).HasColumnName("service_id");
+        builder.Property(x => x.Key).HasColumnName("key").HasMaxLength(100).IsRequired();
+        builder.Property(x => x.Revision).HasColumnName("revision").IsConcurrencyToken();
+        builder.HasIndex(x => new { x.ServiceId, x.Key }).IsUnique();
+        builder.HasAlternateKey(x => new { x.Id, x.ServiceId });
+        builder.HasOne(x => x.Service).WithMany().HasForeignKey(x => x.ServiceId).OnDelete(DeleteBehavior.Restrict);
+        builder.Property(x => x.Created).HasColumnName("created");
+        builder.Property(x => x.Updated).HasColumnName("updated");
+        builder.OwnsMany(x => x.Variables, v =>
+        {
+            v.ToJson("variables");
+            v.Property(x => x.Name).HasJsonPropertyName("name");
+            v.Property(x => x.Required).HasJsonPropertyName("required");
+        });
+    }
+}

HrynCo.NotificationService.DAL.EF/Configurations/EmailTemplateEntityConfiguration.cs

@@ -4,53 +4,27 @@ using Microsoft.EntityFrameworkCore.Metadata.Builders;
 
 namespace HrynCo.NotificationService.DAL.EF.Configurations;
 
-internal class EmailTemplateEntityConfiguration : IEntityTypeConfiguration<EmailTemplateEntity>
+internal sealed class EmailTemplateEntityConfiguration : IEntityTypeConfiguration<EmailTemplateEntity>
 {
     public void Configure(EntityTypeBuilder<EmailTemplateEntity> builder)
     {
         builder.ToTable("email_templates");
-
         builder.HasKey(x => x.Id);
         builder.Property(x => x.Id).HasColumnName("id");
-
+        builder.Property(x => x.DefinitionId).HasColumnName("definition_id");
-        builder.Property(x => x.ServiceName)
+        builder.Property(x => x.ServiceId).HasColumnName("service_id");
-            .HasColumnName("service_name")
+        builder.Property(x => x.ServiceLanguageId).HasColumnName("service_language_id");
-            .IsRequired()
+        builder.HasIndex(x => new { x.DefinitionId, x.ServiceLanguageId }).IsUnique();
-            .HasMaxLength(100);
+        builder.HasOne(x => x.Definition).WithMany(x => x.Languages)
-
+            .HasForeignKey(x => new { x.DefinitionId, x.ServiceId })
-        builder.Property(x => x.Key)
+            .HasPrincipalKey(x => new { x.Id, x.ServiceId }).OnDelete(DeleteBehavior.Cascade);
-            .HasColumnName("key")
+        builder.HasOne(x => x.ServiceLanguage).WithMany()
-            .IsRequired()
+            .HasForeignKey(x => new { x.ServiceLanguageId, x.ServiceId })
-            .HasMaxLength(100);
+            .HasPrincipalKey(x => new { x.Id, x.ServiceId }).OnDelete(DeleteBehavior.Restrict);
-
+        builder.Property(x => x.Subject).HasColumnName("subject").IsRequired();
-        builder.Property(x => x.LanguageCode)
+        builder.Property(x => x.HtmlBody).HasColumnName("html_body").IsRequired();
-            .HasColumnName("language_code")
+        builder.Property(x => x.TextBody).HasColumnName("text_body").IsRequired();
-            .IsRequired()
-            .HasMaxLength(10);
-
-        builder.HasIndex(x => new { x.ServiceName, x.Key, x.LanguageCode })
-            .IsUnique();
-
-        builder.Property(x => x.Subject)
-            .HasColumnName("subject")
-            .IsRequired();
-
-        builder.Property(x => x.HtmlBody)
-            .HasColumnName("html_body")
-            .IsRequired();
-
-        builder.Property(x => x.TextBody)
-            .HasColumnName("text_body")
-            .IsRequired();
-
         builder.Property(x => x.Created).HasColumnName("created");
         builder.Property(x => x.Updated).HasColumnName("updated");
-
-        builder.OwnsMany(x => x.Variables, v =>
-        {
-            v.ToJson("variables");
-            v.Property(x => x.Name).HasJsonPropertyName("name");
-            v.Property(x => x.Required).HasJsonPropertyName("required");
-        });
     }
 }

HrynCo.NotificationService.DAL.EF/Configurations/ServiceEntityConfiguration.cs

@@ -0,0 +1,20 @@
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace HrynCo.NotificationService.DAL.EF.Configurations;
+
+internal sealed class ServiceEntityConfiguration : IEntityTypeConfiguration<ServiceEntity>
+{
+    public void Configure(EntityTypeBuilder<ServiceEntity> builder)
+    {
+        builder.ToTable("services");
+        builder.HasKey(x => x.Id);
+        builder.Property(x => x.Id).HasColumnName("id");
+        builder.Property(x => x.Name).HasColumnName("name").HasMaxLength(100).IsRequired();
+        builder.HasIndex(x => x.Name).IsUnique();
+        builder.Property(x => x.Revision).HasColumnName("revision").IsConcurrencyToken();
+        builder.Property(x => x.Created).HasColumnName("created");
+        builder.Property(x => x.Updated).HasColumnName("updated");
+    }
+}

HrynCo.NotificationService.DAL.EF/Configurations/ServiceLanguageEntityConfiguration.cs

@@ -0,0 +1,22 @@
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace HrynCo.NotificationService.DAL.EF.Configurations;
+
+internal sealed class ServiceLanguageEntityConfiguration : IEntityTypeConfiguration<ServiceLanguageEntity>
+{
+    public void Configure(EntityTypeBuilder<ServiceLanguageEntity> builder)
+    {
+        builder.ToTable("service_languages");
+        builder.HasKey(x => x.Id);
+        builder.Property(x => x.Id).HasColumnName("id");
+        builder.Property(x => x.ServiceId).HasColumnName("service_id");
+        builder.Property(x => x.Code).HasColumnName("code").HasMaxLength(10).IsRequired();
+        builder.HasIndex(x => new { x.ServiceId, x.Code }).IsUnique();
+        builder.HasAlternateKey(x => new { x.Id, x.ServiceId });
+        builder.HasOne(x => x.Service).WithMany(x => x.Languages).HasForeignKey(x => x.ServiceId).OnDelete(DeleteBehavior.Restrict);
+        builder.Property(x => x.Created).HasColumnName("created");
+        builder.Property(x => x.Updated).HasColumnName("updated");
+    }
+}

HrynCo.NotificationService.DAL.EF/Entities/EmailTemplateDefinitionEntity.cs

@@ -0,0 +1,13 @@
+using HrynCo.DAL.Abstract.Entities;
+
+namespace HrynCo.NotificationService.DAL.EF.Entities;
+
+internal sealed class EmailTemplateDefinitionEntity : Entity
+{
+    public Guid ServiceId { get; set; }
+    public ServiceEntity Service { get; set; } = null!;
+    public required string Key { get; set; }
+    public Guid Revision { get; set; } = Guid.NewGuid();
+    public List<EmailTemplateVariableData> Variables { get; set; } = [];
+    public List<EmailTemplateEntity> Languages { get; set; } = [];
+}

HrynCo.NotificationService.DAL.EF/Entities/EmailTemplateEntity.cs

@@ -4,17 +4,12 @@ namespace HrynCo.NotificationService.DAL.EF.Entities;
 
 internal class EmailTemplateEntity : Entity
 {
-    public required string ServiceName { get; set; }
+    public Guid DefinitionId { get; set; }
-    public required string Key { get; set; }
+    public EmailTemplateDefinitionEntity Definition { get; set; } = null!;
-    public required string LanguageCode { get; set; }
+    public Guid ServiceId { get; set; }
+    public Guid ServiceLanguageId { get; set; }
+    public ServiceLanguageEntity ServiceLanguage { get; set; } = null!;
     public required string Subject { get; set; }
     public required string HtmlBody { get; set; }
     public required string TextBody { get; set; }
-    public List<EmailTemplateVariableData> Variables { get; set; } = [];
-}
-
-internal class EmailTemplateVariableData
-{
-    public required string Name { get; set; }
-    public bool Required { get; set; }
 }

HrynCo.NotificationService.DAL.EF/Entities/EmailTemplateVariableData.cs

@@ -0,0 +1,7 @@
+namespace HrynCo.NotificationService.DAL.EF.Entities;
+
+internal sealed class EmailTemplateVariableData
+{
+    public required string Name { get; set; }
+    public bool Required { get; set; }
+}

HrynCo.NotificationService.DAL.EF/Entities/ServiceEntity.cs

@@ -0,0 +1,10 @@
+using HrynCo.DAL.Abstract.Entities;
+
+namespace HrynCo.NotificationService.DAL.EF.Entities;
+
+internal sealed class ServiceEntity : Entity
+{
+    public required string Name { get; set; }
+    public Guid Revision { get; set; } = Guid.NewGuid();
+    public List<ServiceLanguageEntity> Languages { get; set; } = [];
+}

HrynCo.NotificationService.DAL.EF/Entities/ServiceLanguageEntity.cs

@@ -0,0 +1,10 @@
+using HrynCo.DAL.Abstract.Entities;
+
+namespace HrynCo.NotificationService.DAL.EF.Entities;
+
+internal sealed class ServiceLanguageEntity : Entity
+{
+    public Guid ServiceId { get; set; }
+    public ServiceEntity Service { get; set; } = null!;
+    public required string Code { get; set; }
+}

HrynCo.NotificationService.DAL.EF/Migrations/20261017072410_EmailTemplateLocalizations.Designer.cs

@@ -0,0 +1,376 @@
+// <auto-generated />
+using System;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace HrynCo.NotificationService.DAL.EF.Migrations
+{
+    [DbContext(typeof(NotificationDbContext))]
+    [Migration("20261017072410_EmailTemplateLocalizations")]
+    partial class EmailTemplateLocalizations
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.7")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<int?>("DailyLimit")
+                        .HasColumnType("integer")
+                        .HasColumnName("daily_limit");
+
+                    b.Property<int>("EmailChannelType")
+                        .HasColumnType("integer")
+                        .HasColumnName("provider_type");
+
+                    b.Property<bool>("IsActive")
+                        .HasColumnType("boolean")
+                        .HasColumnName("is_active");
+
+                    b.Property<int?>("MonthlyLimit")
+                        .HasColumnType("integer")
+                        .HasColumnName("monthly_limit");
+
+                    b.Property<int>("Priority")
+                        .HasColumnType("integer")
+                        .HasColumnName("priority");
+
+                    b.Property<string>("ServiceName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("service_name");
+
+                    b.Property<string>("SettingsJson")
+                        .IsRequired()
+                        .HasColumnType("jsonb")
+                        .HasColumnName("settings");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.Property<int>("WarnThresholdPercent")
+                        .HasColumnType("integer")
+                        .HasColumnName("warn_threshold_percent");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ServiceName", "Priority");
+
+                    b.ToTable("email_channels", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelUsageEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("date")
+                        .HasColumnName("date");
+
+                    b.Property<Guid>("ProviderId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("provider_id");
+
+                    b.Property<int>("SentCount")
+                        .HasColumnType("integer")
+                        .HasColumnName("sent_count");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ProviderId", "Date")
+                        .IsUnique();
+
+                    b.ToTable("email_channel_usage", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<string>("Key")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("key");
+
+                    b.Property<Guid>("Revision")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid")
+                        .HasColumnName("revision");
+
+                    b.Property<Guid>("ServiceId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("service_id");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ServiceId", "Key")
+                        .IsUnique();
+
+                    b.ToTable("email_template_definitions", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<Guid>("DefinitionId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("definition_id");
+
+                    b.Property<string>("HtmlBody")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("html_body");
+
+                    b.Property<Guid>("ServiceId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("service_id");
+
+                    b.Property<Guid>("ServiceLanguageId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("service_language_id");
+
+                    b.Property<string>("Subject")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("subject");
+
+                    b.Property<string>("TextBody")
+                        .IsRequired()
+                        .HasColumnType("text")
+                        .HasColumnName("text_body");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("DefinitionId", "ServiceId");
+
+                    b.HasIndex("DefinitionId", "ServiceLanguageId")
+                        .IsUnique();
+
+                    b.HasIndex("ServiceLanguageId", "ServiceId");
+
+                    b.ToTable("email_templates", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("name");
+
+                    b.Property<Guid>("Revision")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid")
+                        .HasColumnName("revision");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Name")
+                        .IsUnique();
+
+                    b.ToTable("services", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceLanguageEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Code")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("character varying(10)")
+                        .HasColumnName("code");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<Guid>("ServiceId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("service_id");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ServiceId", "Code")
+                        .IsUnique();
+
+                    b.ToTable("service_languages", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelUsageEntity", b =>
+                {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelEntity", null)
+                        .WithMany("UsageRecords")
+                        .HasForeignKey("ProviderId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", b =>
+                {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", "Service")
+                        .WithMany()
+                        .HasForeignKey("ServiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.OwnsMany("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateVariableData", "Variables", b1 =>
+                        {
+                            b1.Property<Guid>("EmailTemplateDefinitionEntityId");
+
+                            b1.Property<int>("__synthesizedOrdinal")
+                                .ValueGeneratedOnAdd();
+
+                            b1.Property<string>("Name")
+                                .IsRequired()
+                                .HasJsonPropertyName("name");
+
+                            b1.Property<bool>("Required")
+                                .HasJsonPropertyName("required");
+
+                            b1.HasKey("EmailTemplateDefinitionEntityId", "__synthesizedOrdinal");
+
+                            b1.ToTable("email_template_definitions");
+
+                            b1
+                                .ToJson("variables")
+                                .HasColumnType("jsonb");
+
+                            b1.WithOwner()
+                                .HasForeignKey("EmailTemplateDefinitionEntityId");
+                        });
+
+                    b.Navigation("Service");
+
+                    b.Navigation("Variables");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateEntity", b =>
+                {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", "Definition")
+                        .WithMany("Languages")
+                        .HasForeignKey("DefinitionId", "ServiceId")
+                        .HasPrincipalKey("Id", "ServiceId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.ServiceLanguageEntity", "ServiceLanguage")
+                        .WithMany()
+                        .HasForeignKey("ServiceLanguageId", "ServiceId")
+                        .HasPrincipalKey("Id", "ServiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Definition");
+
+                    b.Navigation("ServiceLanguage");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceLanguageEntity", b =>
+                {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", "Service")
+                        .WithMany("Languages")
+                        .HasForeignKey("ServiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Service");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelEntity", b =>
+                {
+                    b.Navigation("UsageRecords");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", b =>
+                {
+                    b.Navigation("Languages");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", b =>
+                {
+                    b.Navigation("Languages");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

HrynCo.NotificationService.DAL.EF/Migrations/20261017072410_EmailTemplateLocalizations.cs

@@ -0,0 +1,284 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace HrynCo.NotificationService.DAL.EF.Migrations;
+
+public partial class EmailTemplateLocalizations : Migration
+{
+    protected override void Up(MigrationBuilder migrationBuilder)
+    {
+        migrationBuilder.Sql(SourceLayoutGuard());
+        migrationBuilder.Sql("DO $upgrade$ BEGIN IF (SELECT layout FROM it1601_migration_origin) = 'flat' THEN\n"
+            + FlatUpgrade() + "\nELSE\n" + InterimUpgrade() + "\nEND IF; END $upgrade$;");
+    }
+
+    protected override void Down(MigrationBuilder migrationBuilder)
+    {
+        migrationBuilder.Sql("""
+            LOCK TABLE email_templates IN ACCESS EXCLUSIVE MODE;
+            DO $$ BEGIN
+                IF EXISTS (SELECT 1 FROM "__EFMigrationsHistory" WHERE "MigrationId" = '20261017070315_EmailTemplateLocalizations') THEN
+                    RAISE EXCEPTION 'Cannot downgrade an interim-origin database to the flat legacy model. Restore a verified backup instead.';
+                END IF;
+                IF EXISTS (SELECT 1 FROM email_template_definitions d WHERE NOT EXISTS (SELECT 1 FROM email_templates t WHERE t.definition_id = d.id))
+                   OR EXISTS (SELECT 1 FROM service_languages l WHERE NOT EXISTS (SELECT 1 FROM email_templates t WHERE t.service_language_id = l.id))
+                   OR EXISTS (SELECT 1 FROM services s WHERE NOT EXISTS (SELECT 1 FROM email_templates t WHERE t.service_id = s.id)) THEN
+                    RAISE EXCEPTION 'Cannot downgrade catalog-only data or empty definitions to the legacy model. Restore a verified backup instead.';
+                END IF;
+            END $$;
+            ALTER TABLE email_templates ADD COLUMN service_name varchar(100), ADD COLUMN key varchar(100),
+                ADD COLUMN language_code varchar(10), ADD COLUMN variables jsonb;
+            UPDATE email_templates t SET service_name = s.name, key = d.key, variables = d.variables, language_code = l.code
+                FROM email_template_definitions d JOIN services s ON s.id = d.service_id
+                    JOIN service_languages l ON l.service_id = s.id
+                WHERE d.id = t.definition_id AND l.id = t.service_language_id;
+            ALTER TABLE email_templates ALTER COLUMN service_name SET NOT NULL, ALTER COLUMN key SET NOT NULL, ALTER COLUMN language_code SET NOT NULL;
+            ALTER TABLE email_templates DROP COLUMN definition_id, DROP COLUMN service_id, DROP COLUMN service_language_id;
+            DROP TABLE email_template_definitions;
+            DROP TABLE service_languages;
+            DROP TABLE services;
+            CREATE UNIQUE INDEX "IX_email_templates_service_name_key_language_code" ON email_templates(service_name, key, language_code);
+            """);
+    }
+
+    private static string FlatUpgrade() => """
+            DO $audit$
+            DECLARE row_record record;
+            BEGIN
+                FOR row_record IN SELECT id, service_name, key, language_code, variables FROM email_templates LOOP
+                    IF btrim(row_record.service_name) = '' OR btrim(row_record.key) = ''
+                       OR btrim(row_record.language_code) = '' OR row_record.variables IS NULL
+                       OR jsonb_typeof(row_record.variables) <> 'array' THEN
+                        RAISE EXCEPTION 'Invalid template identity or variables array: service=%, key=%, language=%, id=%',
+                            row_record.service_name, row_record.key, row_record.language_code, row_record.id;
+                    END IF;
+                    IF EXISTS (SELECT 1 FROM jsonb_array_elements(row_record.variables) v
+                        WHERE jsonb_typeof(v) <> 'object'
+                           OR jsonb_typeof(v->'name') IS DISTINCT FROM 'string'
+                           OR btrim(v->>'name') = ''
+                           OR jsonb_typeof(v->'required') IS DISTINCT FROM 'boolean'
+                           OR (v - 'name' - 'required') <> '{}'::jsonb) THEN
+                        RAISE EXCEPTION 'Invalid variables shape: service=%, key=%, language=%, id=%',
+                            row_record.service_name, row_record.key, row_record.language_code, row_record.id;
+                    END IF;
+                    IF EXISTS (SELECT 1 FROM jsonb_array_elements(row_record.variables) v GROUP BY v->>'name' HAVING count(*) > 1) THEN
+                        RAISE EXCEPTION 'Duplicate variable names: service=%, key=%, language=%, id=%',
+                            row_record.service_name, row_record.key, row_record.language_code, row_record.id;
+                    END IF;
+                END LOOP;
+            END $audit$;
+            CREATE TEMP TABLE template_contract_audit ON COMMIT DROP AS
+                SELECT t.*, COALESCE((SELECT jsonb_agg(v ORDER BY v->>'name')
+                    FROM jsonb_array_elements(t.variables) v), '[]'::jsonb) AS contract
+                FROM email_templates t;
+            DO $conflicts$
+            DECLARE conflict_record record;
+            BEGIN
+                SELECT service_name, key, string_agg(language_code || ':' || id::text, ', ' ORDER BY language_code) AS records
+                    INTO conflict_record FROM template_contract_audit
+                    GROUP BY service_name, key HAVING count(DISTINCT contract) > 1 LIMIT 1;
+                IF FOUND THEN
+                    RAISE EXCEPTION 'Conflicting shared variables: service=%, key=%, records=%',
+                        conflict_record.service_name, conflict_record.key, conflict_record.records;
+                END IF;
+            END $conflicts$;
+            CREATE TABLE services (
+                id uuid CONSTRAINT "PK_services" PRIMARY KEY, name varchar(100) NOT NULL, revision uuid NOT NULL,
+                created timestamptz NOT NULL, updated timestamptz NULL);
+            CREATE UNIQUE INDEX "IX_services_name" ON services(name);
+            CREATE TABLE service_languages (
+                id uuid CONSTRAINT "PK_service_languages" PRIMARY KEY, service_id uuid NOT NULL,
+                code varchar(10) NOT NULL, created timestamptz NOT NULL, updated timestamptz NULL,
+                CONSTRAINT "AK_service_languages_id_service_id" UNIQUE(id, service_id),
+                CONSTRAINT "FK_service_languages_services_service_id" FOREIGN KEY(service_id) REFERENCES services(id) ON DELETE RESTRICT);
+            CREATE UNIQUE INDEX "IX_service_languages_service_id_code" ON service_languages(service_id, code);
+            CREATE TABLE email_template_definitions (
+                id uuid CONSTRAINT "PK_email_template_definitions" PRIMARY KEY, service_id uuid NOT NULL,
+                key varchar(100) NOT NULL, revision uuid NOT NULL, variables jsonb NOT NULL,
+                created timestamptz NOT NULL, updated timestamptz NULL,
+                CONSTRAINT "AK_email_template_definitions_id_service_id" UNIQUE(id, service_id),
+                CONSTRAINT "FK_email_template_definitions_services_service_id" FOREIGN KEY(service_id) REFERENCES services(id) ON DELETE RESTRICT);
+            CREATE UNIQUE INDEX "IX_email_template_definitions_service_id_key" ON email_template_definitions(service_id, key);
+            INSERT INTO services(id, name, revision, created)
+                SELECT gen_random_uuid(), service_name, gen_random_uuid(), min(created) FROM email_templates GROUP BY service_name;
+            INSERT INTO service_languages(id, service_id, code, created)
+                SELECT gen_random_uuid(), s.id, t.language_code, min(t.created)
+                FROM email_templates t JOIN services s ON s.name = t.service_name GROUP BY s.id, t.language_code;
+            INSERT INTO email_template_definitions(id, service_id, key, revision, variables, created, updated)
+                SELECT DISTINCT ON (t.service_name, t.key) t.id, s.id, t.key, gen_random_uuid(), t.contract,
+                    min(t.created) OVER (PARTITION BY t.service_name, t.key),
+                    max(t.updated) OVER (PARTITION BY t.service_name, t.key)
+                FROM template_contract_audit t JOIN services s ON s.name = t.service_name
+                ORDER BY t.service_name, t.key, t.id;
+            ALTER TABLE email_templates ADD COLUMN definition_id uuid, ADD COLUMN service_id uuid, ADD COLUMN service_language_id uuid;
+            UPDATE email_templates t SET definition_id = d.id, service_id = s.id, service_language_id = l.id
+                FROM email_template_definitions d JOIN services s ON s.id = d.service_id
+                    JOIN service_languages l ON l.service_id = s.id
+                WHERE t.service_name = s.name AND t.key = d.key AND t.language_code = l.code;
+            ALTER TABLE email_templates ALTER COLUMN definition_id SET NOT NULL,
+                ALTER COLUMN service_id SET NOT NULL, ALTER COLUMN service_language_id SET NOT NULL;
+            ALTER TABLE email_templates ADD CONSTRAINT "FK_email_templates_email_template_definitions_definition_id_se~"
+                FOREIGN KEY (definition_id, service_id) REFERENCES email_template_definitions(id, service_id) ON DELETE CASCADE;
+            ALTER TABLE email_templates ADD CONSTRAINT "FK_email_templates_service_languages_service_language_id_servi~"
+                FOREIGN KEY (service_language_id, service_id) REFERENCES service_languages(id, service_id) ON DELETE RESTRICT;
+            DROP INDEX "IX_email_templates_service_name_key_language_code";
+            ALTER TABLE email_templates DROP COLUMN service_name, DROP COLUMN key, DROP COLUMN variables, DROP COLUMN language_code;
+            CREATE UNIQUE INDEX "IX_email_templates_definition_id_service_language_id" ON email_templates(definition_id, service_language_id);
+            CREATE INDEX "IX_email_templates_definition_id_service_id" ON email_templates(definition_id, service_id);
+            CREATE INDEX "IX_email_templates_service_language_id_service_id" ON email_templates(service_language_id, service_id);
+            """;
+
+    private static string SourceLayoutGuard() => """
+            SET LOCAL search_path = public;
+            DO $layout$
+            DECLARE
+                template_columns text[];
+                service_columns text[];
+                definition_columns text[];
+                source_constraints text[];
+                source_indexes text[];
+                known_interim_history boolean;
+                source_layout text;
+            BEGIN
+                SELECT array_agg(column_name || ':' || udt_name || ':' || coalesce(character_maximum_length::text, '') || ':' || is_nullable ORDER BY column_name)
+                    INTO template_columns FROM information_schema.columns WHERE table_schema = 'public' AND table_name = 'email_templates';
+                SELECT array_agg(column_name || ':' || udt_name || ':' || coalesce(character_maximum_length::text, '') || ':' || is_nullable ORDER BY column_name)
+                    INTO service_columns FROM information_schema.columns WHERE table_schema = 'public' AND table_name = 'services';
+                SELECT array_agg(column_name || ':' || udt_name || ':' || coalesce(character_maximum_length::text, '') || ':' || is_nullable ORDER BY column_name)
+                    INTO definition_columns FROM information_schema.columns WHERE table_schema = 'public' AND table_name = 'email_template_definitions';
+                SELECT EXISTS (SELECT 1 FROM "__EFMigrationsHistory" WHERE "MigrationId" = '20261017070315_EmailTemplateLocalizations') INTO known_interim_history;
+                SELECT array_agg(c.relname || ':' || p.conname || ':' || pg_get_constraintdef(p.oid) ORDER BY c.relname, p.conname)
+                    INTO source_constraints FROM pg_constraint p JOIN pg_class c ON c.oid = p.conrelid
+                    JOIN pg_namespace n ON n.oid = c.relnamespace WHERE n.nspname = 'public'
+                    AND c.relname IN ('services', 'email_template_definitions', 'email_templates');
+                SELECT array_agg(indexdef ORDER BY indexname) INTO source_indexes FROM pg_indexes
+                    WHERE schemaname = 'public' AND tablename IN ('services', 'email_template_definitions', 'email_templates');
+                IF to_regclass('public.service_languages') IS NOT NULL THEN
+                    RAISE EXCEPTION 'Unsupported email-template source layout: service language catalog already exists without the current migration history.';
+                END IF;
+                IF template_columns = ARRAY['created:timestamptz::NO',
+                    'html_body:text::NO',
+                    'id:uuid::NO',
+                    'key:varchar:100:NO',
+                    'language_code:varchar:10:NO',
+                    'service_name:varchar:100:NO',
+                    'subject:text::NO',
+                    'text_body:text::NO',
+                    'updated:timestamptz::YES',
+                    'variables:jsonb::YES']
+                   AND service_columns IS NULL AND definition_columns IS NULL AND NOT known_interim_history
+                   AND source_constraints = ARRAY['email_templates:PK_email_templates:PRIMARY KEY (id)']
+                   AND source_indexes = ARRAY[
+                    'CREATE UNIQUE INDEX "IX_email_templates_service_name_key_language_code" ON public.email_templates USING btree (service_name, key, language_code)',
+                    'CREATE UNIQUE INDEX "PK_email_templates" ON public.email_templates USING btree (id)'] THEN
+                    source_layout := 'flat';
+                ELSIF template_columns = ARRAY['created:timestamptz::NO',
+                    'definition_id:uuid::NO',
+                    'html_body:text::NO',
+                    'id:uuid::NO',
+                    'language_code:varchar:10:NO',
+                    'subject:text::NO',
+                    'text_body:text::NO',
+                    'updated:timestamptz::YES']
+                   AND service_columns = ARRAY['created:timestamptz::NO',
+                    'id:uuid::NO',
+                    'name:varchar:100:NO',
+                    'updated:timestamptz::YES']
+                   AND definition_columns = ARRAY['created:timestamptz::NO',
+                    'id:uuid::NO',
+                    'key:varchar:100:NO',
+                    'revision:uuid::NO',
+                    'service_id:uuid::NO',
+                    'updated:timestamptz::YES',
+                    'variables:jsonb::NO']
+                   AND known_interim_history
+                   AND source_constraints = ARRAY[
+                    'email_template_definitions:email_template_definitions_pkey:PRIMARY KEY (id)',
+                    'email_template_definitions:email_template_definitions_service_id_fkey:FOREIGN KEY (service_id) REFERENCES services(id) ON DELETE RESTRICT',
+                    'email_templates:FK_email_templates_email_template_definitions_definition_id:FOREIGN KEY (definition_id) REFERENCES email_template_definitions(id) ON DELETE CASCADE',
+                    'email_templates:PK_email_templates:PRIMARY KEY (id)',
+                    'services:services_pkey:PRIMARY KEY (id)']
+                   AND source_indexes = ARRAY[
+                    'CREATE UNIQUE INDEX "IX_email_template_definitions_service_id_key" ON public.email_template_definitions USING btree (service_id, key)',
+                    'CREATE UNIQUE INDEX "IX_email_templates_definition_id_language_code" ON public.email_templates USING btree (definition_id, language_code)',
+                    'CREATE UNIQUE INDEX "IX_services_name" ON public.services USING btree (name)',
+                    'CREATE UNIQUE INDEX "PK_email_templates" ON public.email_templates USING btree (id)',
+                    'CREATE UNIQUE INDEX email_template_definitions_pkey ON public.email_template_definitions USING btree (id)',
+                    'CREATE UNIQUE INDEX services_pkey ON public.services USING btree (id)'] THEN
+                    source_layout := 'interim';
+                ELSE
+                    RAISE EXCEPTION 'Unsupported email-template source layout or history. Expected the flat legacy schema or the known 20261017070315 interim schema; no changes were made.';
+                END IF;
+                LOCK TABLE email_templates IN ACCESS EXCLUSIVE MODE;
+                IF source_layout = 'interim' THEN
+                    LOCK TABLE services, email_template_definitions IN ACCESS EXCLUSIVE MODE;
+                END IF;
+                CREATE TEMP TABLE it1601_migration_origin (layout text NOT NULL) ON COMMIT DROP;
+                INSERT INTO it1601_migration_origin VALUES (source_layout);
+            END $layout$;
+            """;
+
+    private static string InterimUpgrade() => """
+            DO $interim_audit$
+            DECLARE row_record record;
+            BEGIN
+                IF EXISTS (SELECT 1 FROM services WHERE btrim(name) = '')
+                   OR EXISTS (SELECT 1 FROM email_template_definitions WHERE btrim(key) = '')
+                   OR EXISTS (SELECT 1 FROM email_templates WHERE btrim(language_code) = '') THEN
+                    RAISE EXCEPTION 'Invalid blank identity in interim email-template data; no changes were made.';
+                END IF;
+                IF EXISTS (SELECT 1 FROM email_template_definitions d LEFT JOIN services s ON s.id = d.service_id WHERE s.id IS NULL)
+                   OR EXISTS (SELECT 1 FROM email_templates t LEFT JOIN email_template_definitions d ON d.id = t.definition_id WHERE d.id IS NULL) THEN
+                    RAISE EXCEPTION 'Invalid orphaned reference in interim email-template data; no changes were made.';
+                END IF;
+                FOR row_record IN SELECT d.id, s.name AS service_name, d.key, d.variables FROM email_template_definitions d JOIN services s ON s.id = d.service_id LOOP
+                    IF row_record.variables IS NULL OR jsonb_typeof(row_record.variables) <> 'array' THEN
+                        RAISE EXCEPTION 'Invalid interim shared variables array: service=%, key=%, definition=%', row_record.service_name, row_record.key, row_record.id;
+                    END IF;
+                    IF EXISTS (SELECT 1 FROM jsonb_array_elements(row_record.variables) v
+                        WHERE jsonb_typeof(v) <> 'object'
+                           OR jsonb_typeof(v->'name') IS DISTINCT FROM 'string'
+                           OR btrim(v->>'name') = ''
+                           OR jsonb_typeof(v->'required') IS DISTINCT FROM 'boolean'
+                           OR (v - 'name' - 'required') <> '{}'::jsonb) THEN
+                        RAISE EXCEPTION 'Invalid interim shared variables shape: service=%, key=%, definition=%', row_record.service_name, row_record.key, row_record.id;
+                    END IF;
+                    IF EXISTS (SELECT 1 FROM jsonb_array_elements(row_record.variables) v GROUP BY v->>'name' HAVING count(*) > 1) THEN
+                        RAISE EXCEPTION 'Duplicate interim shared variable names: service=%, key=%, definition=%', row_record.service_name, row_record.key, row_record.id;
+                    END IF;
+                END LOOP;
+            END $interim_audit$;
+            ALTER TABLE services ADD COLUMN revision uuid;
+            UPDATE services SET revision = gen_random_uuid();
+            ALTER TABLE services ALTER COLUMN revision SET NOT NULL;
+            ALTER TABLE services RENAME CONSTRAINT services_pkey TO "PK_services";
+            ALTER TABLE email_template_definitions RENAME CONSTRAINT email_template_definitions_pkey TO "PK_email_template_definitions";
+            ALTER TABLE email_template_definitions RENAME CONSTRAINT email_template_definitions_service_id_fkey TO "FK_email_template_definitions_services_service_id";
+            ALTER TABLE email_template_definitions ADD CONSTRAINT "AK_email_template_definitions_id_service_id" UNIQUE(id, service_id);
+            CREATE TABLE service_languages (
+                id uuid CONSTRAINT "PK_service_languages" PRIMARY KEY, service_id uuid NOT NULL,
+                code varchar(10) NOT NULL, created timestamptz NOT NULL, updated timestamptz NULL,
+                CONSTRAINT "AK_service_languages_id_service_id" UNIQUE(id, service_id),
+                CONSTRAINT "FK_service_languages_services_service_id" FOREIGN KEY(service_id) REFERENCES services(id) ON DELETE RESTRICT);
+            CREATE UNIQUE INDEX "IX_service_languages_service_id_code" ON service_languages(service_id, code);
+            INSERT INTO service_languages(id, service_id, code, created, updated)
+                SELECT gen_random_uuid(), d.service_id, t.language_code, min(t.created), max(t.updated)
+                FROM email_templates t JOIN email_template_definitions d ON d.id = t.definition_id GROUP BY d.service_id, t.language_code;
+            ALTER TABLE email_templates ADD COLUMN service_id uuid, ADD COLUMN service_language_id uuid;
+            UPDATE email_templates t SET service_id = d.service_id, service_language_id = l.id
+                FROM email_template_definitions d JOIN service_languages l ON l.service_id = d.service_id
+                WHERE t.definition_id = d.id AND t.language_code = l.code;
+            ALTER TABLE email_templates ALTER COLUMN service_id SET NOT NULL, ALTER COLUMN service_language_id SET NOT NULL;
+            ALTER TABLE email_templates ADD CONSTRAINT "FK_email_templates_email_template_definitions_definition_id_se~"
+                FOREIGN KEY (definition_id, service_id) REFERENCES email_template_definitions(id, service_id) ON DELETE CASCADE;
+            ALTER TABLE email_templates ADD CONSTRAINT "FK_email_templates_service_languages_service_language_id_servi~"
+                FOREIGN KEY (service_language_id, service_id) REFERENCES service_languages(id, service_id) ON DELETE RESTRICT;
+            ALTER TABLE email_templates DROP CONSTRAINT "FK_email_templates_email_template_definitions_definition_id";
+            DROP INDEX "IX_email_templates_definition_id_language_code";
+            ALTER TABLE email_templates DROP COLUMN language_code;
+            CREATE UNIQUE INDEX "IX_email_templates_definition_id_service_language_id" ON email_templates(definition_id, service_language_id);
+            CREATE INDEX "IX_email_templates_definition_id_service_id" ON email_templates(definition_id, service_id);
+            CREATE INDEX "IX_email_templates_service_language_id_service_id" ON email_templates(service_language_id, service_id);
+            """;
+}

HrynCo.NotificationService.DAL.EF/Migrations/NotificationDbContextModelSnapshot.cs

@@ -17,7 +17,7 @@ namespace HrynCo.NotificationService.DAL.EF.Migrations
         {
 #pragma warning disable 612, 618
             modelBuilder
-                .HasAnnotation("ProductVersion", "9.0.5")
+                .HasAnnotation("ProductVersion", "10.0.7")
                 .HasAnnotation("Relational:MaxIdentifierLength", 63);
 
             NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
@@ -114,6 +114,44 @@ namespace HrynCo.NotificationService.DAL.EF.Migrations
                     b.ToTable("email_channel_usage", (string)null);
                 });
 
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<string>("Key")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("key");
+
+                    b.Property<Guid>("Revision")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid")
+                        .HasColumnName("revision");
+
+                    b.Property<Guid>("ServiceId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("service_id");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ServiceId", "Key")
+                        .IsUnique();
+
+                    b.ToTable("email_template_definitions", (string)null);
+                });
+
             modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateEntity", b =>
                 {
                     b.Property<Guid>("Id")
@@ -125,28 +163,22 @@ namespace HrynCo.NotificationService.DAL.EF.Migrations
                         .HasColumnType("timestamp with time zone")
                         .HasColumnName("created");
 
+                    b.Property<Guid>("DefinitionId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("definition_id");
+
                     b.Property<string>("HtmlBody")
                         .IsRequired()
                         .HasColumnType("text")
                         .HasColumnName("html_body");
 
-                    b.Property<string>("Key")
+                    b.Property<Guid>("ServiceId")
-                        .IsRequired()
+                        .HasColumnType("uuid")
-                        .HasMaxLength(100)
+                        .HasColumnName("service_id");
-                        .HasColumnType("character varying(100)")
-                        .HasColumnName("key");
 
-                    b.Property<string>("LanguageCode")
+                    b.Property<Guid>("ServiceLanguageId")
-                        .IsRequired()
+                        .HasColumnType("uuid")
-                        .HasMaxLength(10)
+                        .HasColumnName("service_language_id");
-                        .HasColumnType("character varying(10)")
-                        .HasColumnName("language_code");
-
-                    b.Property<string>("ServiceName")
-                        .IsRequired()
-                        .HasMaxLength(100)
-                        .HasColumnType("character varying(100)")
-                        .HasColumnName("service_name");
 
                     b.Property<string>("Subject")
                         .IsRequired()
@@ -164,12 +196,83 @@ namespace HrynCo.NotificationService.DAL.EF.Migrations
 
                     b.HasKey("Id");
 
-                    b.HasIndex("ServiceName", "Key", "LanguageCode")
+                    b.HasIndex("DefinitionId", "ServiceId");
+
+                    b.HasIndex("DefinitionId", "ServiceLanguageId")
                         .IsUnique();
 
+                    b.HasIndex("ServiceLanguageId", "ServiceId");
+
                     b.ToTable("email_templates", (string)null);
                 });
 
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)")
+                        .HasColumnName("name");
+
+                    b.Property<Guid>("Revision")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid")
+                        .HasColumnName("revision");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Name")
+                        .IsUnique();
+
+                    b.ToTable("services", (string)null);
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceLanguageEntity", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Code")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("character varying(10)")
+                        .HasColumnName("code");
+
+                    b.Property<DateTimeOffset>("Created")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("created");
+
+                    b.Property<Guid>("ServiceId")
+                        .HasColumnType("uuid")
+                        .HasColumnName("service_id");
+
+                    b.Property<DateTimeOffset?>("Updated")
+                        .HasColumnType("timestamp with time zone")
+                        .HasColumnName("updated");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ServiceId", "Code")
+                        .IsUnique();
+
+                    b.ToTable("service_languages", (string)null);
+                });
+
             modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelUsageEntity", b =>
                 {
                     b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelEntity", null)
@@ -179,43 +282,91 @@ namespace HrynCo.NotificationService.DAL.EF.Migrations
                         .IsRequired();
                 });
 
-            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateEntity", b =>
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", b =>
                 {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", "Service")
+                        .WithMany()
+                        .HasForeignKey("ServiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
                     b.OwnsMany("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateVariableData", "Variables", b1 =>
                         {
-                            b1.Property<Guid>("EmailTemplateEntityId")
+                            b1.Property<Guid>("EmailTemplateDefinitionEntityId");
-                                .HasColumnType("uuid");
 
                             b1.Property<int>("__synthesizedOrdinal")
-                                .ValueGeneratedOnAdd()
+                                .ValueGeneratedOnAdd();
-                                .HasColumnType("integer");
 
                             b1.Property<string>("Name")
                                 .IsRequired()
-                                .HasColumnType("text")
+                                .HasJsonPropertyName("name");
-                                .HasAnnotation("Relational:JsonPropertyName", "name");
 
                             b1.Property<bool>("Required")
-                                .HasColumnType("boolean")
+                                .HasJsonPropertyName("required");
-                                .HasAnnotation("Relational:JsonPropertyName", "required");
 
-                            b1.HasKey("EmailTemplateEntityId", "__synthesizedOrdinal");
+                            b1.HasKey("EmailTemplateDefinitionEntityId", "__synthesizedOrdinal");
 
-                            b1.ToTable("email_templates");
+                            b1.ToTable("email_template_definitions");
 
-                            b1.ToJson("variables");
+                            b1
+                                .ToJson("variables")
+                                .HasColumnType("jsonb");
 
                             b1.WithOwner()
-                                .HasForeignKey("EmailTemplateEntityId");
+                                .HasForeignKey("EmailTemplateDefinitionEntityId");
                         });
 
+                    b.Navigation("Service");
+
                     b.Navigation("Variables");
                 });
 
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateEntity", b =>
+                {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", "Definition")
+                        .WithMany("Languages")
+                        .HasForeignKey("DefinitionId", "ServiceId")
+                        .HasPrincipalKey("Id", "ServiceId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.ServiceLanguageEntity", "ServiceLanguage")
+                        .WithMany()
+                        .HasForeignKey("ServiceLanguageId", "ServiceId")
+                        .HasPrincipalKey("Id", "ServiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Definition");
+
+                    b.Navigation("ServiceLanguage");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceLanguageEntity", b =>
+                {
+                    b.HasOne("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", "Service")
+                        .WithMany("Languages")
+                        .HasForeignKey("ServiceId")
+                        .OnDelete(DeleteBehavior.Restrict)
+                        .IsRequired();
+
+                    b.Navigation("Service");
+                });
+
             modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailChannelEntity", b =>
                 {
                     b.Navigation("UsageRecords");
                 });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.EmailTemplateDefinitionEntity", b =>
+                {
+                    b.Navigation("Languages");
+                });
+
+            modelBuilder.Entity("HrynCo.NotificationService.DAL.EF.Entities.ServiceEntity", b =>
+                {
+                    b.Navigation("Languages");
+                });
 #pragma warning restore 612, 618
         }
     }

HrynCo.NotificationService.DAL.EF/NotificationDbContext.cs

@@ -10,6 +10,9 @@ public class NotificationDbContext : DbContext
     {
     }
 
+    internal DbSet<ServiceLanguageEntity> ServiceLanguages => Set<ServiceLanguageEntity>();
+    internal DbSet<ServiceEntity> Services => Set<ServiceEntity>();
+    internal DbSet<EmailTemplateDefinitionEntity> TemplateDefinitions => Set<EmailTemplateDefinitionEntity>();
     internal DbSet<EmailTemplateEntity> Templates => Set<EmailTemplateEntity>();
     internal DbSet<EmailChannelEntity> Providers => Set<EmailChannelEntity>();
     internal DbSet<EmailChannelUsageEntity> EmailChannelUsage => Set<EmailChannelUsageEntity>();

HrynCo.NotificationService.DAL.EF/Repositories/EmailChannelRepository.cs

@@ -54,7 +54,7 @@ internal sealed class EmailChannelRepository : NotificationBaseRepository<EmailC
 
     public async Task<EmailChannel?> GetByIdAsync(Guid id, CancellationToken ct = default)
     {
-        EmailChannelEntity? entity = await EfRepository.GetByIdAsync(id);
+        EmailChannelEntity? entity = await EfRepository.Get().AsNoTracking().SingleOrDefaultAsync(c => c.Id == id, ct);
         return entity is null ? null : MapToDomain(entity);
     }
 

HrynCo.NotificationService.DAL.EF/Repositories/EmailTemplateRepository.cs

@@ -1,91 +1,324 @@
 using HrynCo.NotificationService.DAL.Abstract.Repositories;
 using HrynCo.NotificationService.DAL.Abstract.Templates;
-using HrynCo.NotificationService.DAL.EF.Core;
 using HrynCo.NotificationService.DAL.EF.Entities;
 using Microsoft.EntityFrameworkCore;
 
 namespace HrynCo.NotificationService.DAL.EF.Repositories;
 
-internal sealed class EmailTemplateRepository
+internal sealed class EmailTemplateRepository(NotificationDbContext db, TemplateMutationRunner mutations)
-    : NotificationBaseRepository<EmailTemplateEntity>, IEmailTemplateRepository
+    : IEmailTemplateRepository, IEmailTemplateDefinitionRepository
 {
-    public EmailTemplateRepository(NotificationDbContext dbContext) : base(dbContext)
+    private IQueryable<EmailTemplateEntity> Languages => db.Templates
+        .Include(t => t.Definition).ThenInclude(d => d.Service).Include(t => t.ServiceLanguage);
+    private IQueryable<EmailTemplateDefinitionEntity> Definitions => db.TemplateDefinitions
+        .Include(d => d.Service).ThenInclude(s => s.Languages)
+        .Include(d => d.Languages).ThenInclude(t => t.ServiceLanguage);
+
+    public async Task<IReadOnlyList<EmailTemplate>> GetAllAsync(string? serviceName = null, string? key = null, CancellationToken ct = default)
     {
+        var query = Languages.AsNoTracking();
+        if (!string.IsNullOrWhiteSpace(serviceName))
+            query = query.Where(t => t.Definition.Service.Name == serviceName);
+        if (!string.IsNullOrWhiteSpace(key))
+            query = query.Where(t => t.Definition.Key == key);
+        var entities = await query.OrderBy(t => t.Definition.Service.Name).ThenBy(t => t.Definition.Key)
+            .ThenBy(t => t.ServiceLanguage.Code).ToListAsync(ct);
+        return entities.Select(MapLanguage).ToList();
     }
 
-    public async Task<IReadOnlyList<EmailTemplate>> GetAllAsync(CancellationToken ct = default)
+    public Task<IReadOnlyList<EmailTemplate>> GetByServiceAsync(string serviceName, CancellationToken ct = default) =>
-    {
+        GetAllAsync(serviceName, ct: ct);
-        List<EmailTemplateEntity> entities = await EfRepository.Get()
-            .AsNoTracking()
-            .ToListAsync(ct);
-        return entities.Select(MapToDomain).ToList();
-    }
-
-    public async Task<IReadOnlyList<EmailTemplate>> GetByServiceAsync(string serviceName, CancellationToken ct = default)
-    {
-        List<EmailTemplateEntity> entities = await EfRepository.Get()
-            .AsNoTracking()
-            .Where(x => x.ServiceName == serviceName)
-            .ToListAsync(ct);
-
-        return entities.Select(MapToDomain).ToList();
-    }
 
     public async Task<EmailTemplate?> GetAsync(string serviceName, string key, string languageCode, CancellationToken ct = default)
     {
-        EmailTemplateEntity? entity = await EfRepository.Get()
+        var code = languageCode;
-            .AsNoTracking()
+        var entity = await Languages.AsNoTracking().SingleOrDefaultAsync(t =>
-            .FirstOrDefaultAsync(
+            t.Definition.Service.Name == serviceName && t.Definition.Key == key && t.ServiceLanguage.Code == code, ct);
-                x => x.ServiceName == serviceName && x.Key == key && x.LanguageCode == languageCode, ct);
+        return entity is null ? null : MapLanguage(entity);
-
-        return entity is null ? null : MapToDomain(entity);
     }
 
-    public Task AddAsync(EmailTemplate EmailTemplate, CancellationToken ct = default)
+    public async Task<EmailTemplateDefinition?> GetDefinitionAsync(string serviceName, string key, CancellationToken ct = default)
     {
-        return EfRepository.AddAsync(MapToEntity(EmailTemplate));
+        var entity = await Definitions.AsNoTracking().SingleOrDefaultAsync(d => d.Service.Name == serviceName && d.Key == key, ct);
+        return entity is null ? null : MapDefinition(entity);
     }
 
-    public Task UpdateAsync(EmailTemplate EmailTemplate, CancellationToken ct = default)
+    public async Task<EmailTemplateDefinition?> GetDefinitionAsync(Guid serviceId, string key, CancellationToken ct = default)
     {
-        EmailTemplateEntity entity = MapToEntity(EmailTemplate);
+        var entity = await Definitions.AsNoTracking().SingleOrDefaultAsync(d => d.ServiceId == serviceId && d.Key == key, ct);
-        entity.Updated = DateTimeOffset.UtcNow;
+        return entity is null ? null : MapDefinition(entity);
-        return EfRepository.UpdateAsync(entity);
     }
 
-    public async Task DeleteAsync(EmailTemplate EmailTemplate, CancellationToken ct = default)
+    public async Task<EmailTemplateDefinition?> UpsertDefinitionAsync(EmailTemplateDefinitionPatch patch, CancellationToken ct = default)
+    {
+        EmailTemplateDefinitionEntity? saved = null;
+        await mutations.ExecuteAsync(async () =>
+        {
+            var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Id == patch.ServiceId, ct);
+            if (service is null)
+                return;
+            ValidatePatch(patch, service);
+            var entity = await LoadForUpsertAsync(patch, service, ct);
+            entity.Variables = MapVariables(patch.Variables);
+            var removed = patch.RemoveLanguageCodes.ToHashSet(StringComparer.Ordinal);
+            db.Templates.RemoveRange(entity.Languages.Where(t => removed.Contains(t.ServiceLanguage.Code)));
+            // Omitted translations are retained. Only explicitly supplied content is changed.
+            UpsertLanguages(entity, patch.Translations);
+            Touch(entity);
+            saved = entity;
+        }, ct);
+        return saved is null ? null : MapDefinition(saved);
+    }
+
+    private async Task<EmailTemplateDefinitionEntity> LoadForUpsertAsync(EmailTemplateDefinitionPatch patch, ServiceEntity service, CancellationToken ct)
+    {
+        var entity = await Definitions.SingleOrDefaultAsync(d => d.ServiceId == patch.ServiceId && d.Key == patch.Key, ct);
+        if (patch.Revision is null)
         {
-        EmailTemplateEntity? entity = await EfRepository.Get()
-            .FirstOrDefaultAsync(x => x.Id == EmailTemplate.Id, ct);
             if (entity is not null)
-            await EfRepository.DeleteAsync(entity);
+                throw new EmailTemplateWriteException("A definition with this service and key already exists. Read its revision before updating.");
+            entity = new EmailTemplateDefinitionEntity { Service = service, ServiceId = service.Id, Key = patch.Key, Created = DateTimeOffset.UtcNow };
+            db.TemplateDefinitions.Add(entity);
+            return entity;
+        }
+        if (entity is null || entity.Revision != patch.Revision)
+            throw new EmailTemplateWriteException("The definition is missing or its revision changed. Read it again before updating.");
+        return entity;
     }
 
-    private static EmailTemplate MapToDomain(EmailTemplateEntity e) => new()
+    private static void ValidatePatch(EmailTemplateDefinitionPatch patch, ServiceEntity service)
     {
-        Id = e.Id,
+        EmailTemplateValidation.ValidateDefinition(new EmailTemplateDefinition
-        ServiceName = e.ServiceName,
+        {
-        Key = e.Key,
+            ServiceId = service.Id, ServiceName = service.Name, Key = patch.Key,
-        LanguageCode = e.LanguageCode,
+            Variables = patch.Variables, Languages = patch.Translations
-        Subject = e.Subject,
+        });
-        HtmlBody = e.HtmlBody,
+        if (patch.Revision == Guid.Empty)
-        TextBody = e.TextBody,
+            throw new EmailTemplateWriteException("Revision must be null for creation or a nonempty revision from the last read for update.", false);
-        Variables = e.Variables.Select(v => new EmailTemplateVariable { Name = v.Name, Required = v.Required }).ToList(),
+        var removed = patch.RemoveLanguageCodes;
-        Created = e.Created,
+        if (removed.Any(string.IsNullOrWhiteSpace) || removed.Distinct(StringComparer.Ordinal).Count() != removed.Count)
-        Updated = e.Updated
+            throw new EmailTemplateWriteException("removeLanguageCodes must contain unique nonblank language codes.", false);
+        var supplied = patch.Translations.Select(t => t.LanguageCode).ToHashSet(StringComparer.Ordinal);
+        if (removed.Any(supplied.Contains))
+            throw new EmailTemplateWriteException("A language cannot be supplied and removed in the same request.", false);
+        var supported = service.Languages.Select(l => l.Code).ToHashSet(StringComparer.Ordinal);
+        if (supplied.Concat(removed).Any(code => !supported.Contains(code)))
+            throw new EmailTemplateWriteException("Every supplied or removed language must exactly match a code in this service's catalog.", false);
+    }
+
+    public async Task<IReadOnlyList<EmailTemplateDefinition>> GetDefinitionsAsync(Guid serviceId, CancellationToken ct = default)
+    {
+        var entities = await Definitions.AsNoTracking().Where(d => d.ServiceId == serviceId).OrderBy(d => d.Key).ToListAsync(ct);
+        return entities.Select(MapDefinition).ToList();
+    }
+
+    public async Task<bool> DeleteDefinitionAsync(Guid serviceId, string key, Guid revision, CancellationToken ct = default)
+    {
+        var removed = false;
+        await mutations.ExecuteAsync(async () =>
+        {
+            if (string.IsNullOrWhiteSpace(key) || key.Length > 100 || revision == Guid.Empty)
+                throw new EmailTemplateWriteException("An exact key (at most 100 characters) and a nonempty revision are required.", false);
+            var definition = await Definitions.SingleOrDefaultAsync(d => d.ServiceId == serviceId && d.Key == key, ct);
+            if (definition is null)
+                return;
+            if (definition.Revision != revision)
+                throw new EmailTemplateWriteException("The definition revision changed. Read it again before deleting.");
+            db.TemplateDefinitions.Remove(definition);
+            removed = true;
+        }, ct);
+        return removed;
+    }
+
+    public Task AddAsync(EmailTemplate template, CancellationToken ct = default) => mutations.ExecuteAsync(async () =>
+    {
+        ValidateLegacy(template);
+        var definition = await FindDefinitionAsync(template.ServiceName, template.Key, ct);
+        if (definition is null)
+        {
+            await RequireServiceLanguageAsync(template.ServiceName, template.LanguageCode, ct);
+            definition = await CreateDefinitionAsync(template.ServiceName, template.Key, template.Variables, ct);
+        }
+        EnsureMatchingContract(definition, template.Variables);
+        await RequireServiceLanguageAsync(template.ServiceName, template.LanguageCode, ct);
+        var code = template.LanguageCode;
+        if (definition.Languages.Any(t => t.ServiceLanguage.Code == code))
+            throw new EmailTemplateWriteException("This language already exists for the template.");
+        var language = NewLanguage(template, definition);
+        definition.Languages.Add(language);
+        db.Templates.Add(language);
+        Touch(definition);
+    }, ct);
+
+    public Task UpdateAsync(EmailTemplate template, CancellationToken ct = default) => mutations.ExecuteAsync(async () =>
+    {
+        ValidateLegacy(template);
+        var definition = await RequireDefinitionAsync(template.ServiceName, template.Key, ct);
+        EnsureMatchingContract(definition, template.Variables);
+        var language = definition.Languages.SingleOrDefault(t => t.Id == template.Id)
+            ?? throw new EmailTemplateWriteException("The language changed or was removed. Reload the template.");
+        SetContent(language, template);
+        Touch(definition);
+    }, ct);
+
+    public Task DeleteAsync(EmailTemplate template, CancellationToken ct = default) => mutations.ExecuteAsync(async () =>
+    {
+        var definition = await RequireDefinitionAsync(template.ServiceName, template.Key, ct);
+        var language = definition.Languages.SingleOrDefault(t => t.Id == template.Id)
+            ?? throw new EmailTemplateWriteException("The language changed or was removed. Reload the template.");
+        db.Templates.Remove(language);
+        Touch(definition);
+    }, ct);
+
+    public Task SaveDefinitionAsync(EmailTemplateDefinition definition, bool isNew, CancellationToken ct = default) => mutations.ExecuteAsync(async () =>
+    {
+        EmailTemplateValidation.ValidateDefinition(definition);
+        await ValidateServiceLanguagesAsync(definition, ct);
+        var entity = await LoadForSaveAsync(definition, isNew, ct);
+        entity.Variables = MapVariables(definition.Variables);
+        SynchronizeLanguages(entity, definition.Languages);
+        Touch(entity);
+        definition.Id = entity.Id;
+        definition.Revision = entity.Revision;
+    }, ct);
+
+    private async Task<EmailTemplateDefinitionEntity> LoadForSaveAsync(EmailTemplateDefinition model, bool isNew, CancellationToken ct)
+    {
+        var entity = await FindDefinitionAsync(model.ServiceName, model.Key, ct);
+        if (isNew)
+        {
+            if (entity is not null)
+                throw new EmailTemplateWriteException("A template with this service and key already exists.");
+            return await CreateDefinitionAsync(model.ServiceName, model.Key, model.Variables, ct);
+        }
+        if (entity is null || entity.Id != model.Id || entity.Revision != model.Revision)
+            throw new EmailTemplateWriteException("This template changed after you opened it. Reload before saving; your entered values are retained.");
+        return entity;
+    }
+
+    private void SynchronizeLanguages(EmailTemplateDefinitionEntity definition, IReadOnlyList<EmailTemplate> languages)
+    {
+        var codes = languages.Select(t => t.LanguageCode).ToHashSet(StringComparer.Ordinal);
+        db.Templates.RemoveRange(definition.Languages.Where(t => !codes.Contains(t.ServiceLanguage.Code)));
+        UpsertLanguages(definition, languages);
+    }
+
+    private void UpsertLanguages(EmailTemplateDefinitionEntity definition, IReadOnlyList<EmailTemplate> languages)
+    {
+        foreach (var model in languages)
+        {
+            var code = model.LanguageCode;
+            var entity = definition.Languages.SingleOrDefault(t => t.ServiceLanguage.Code == code);
+            if (entity is null)
+            {
+                var language = NewLanguage(model, definition);
+                definition.Languages.Add(language);
+                db.Templates.Add(language);
+            }
+            else
+                SetContent(entity, model);
+        }
+    }
+
+    public async Task<IReadOnlyList<EmailTemplateDefinition>> GetDefinitionsAsync(string? serviceName = null, string? key = null, CancellationToken ct = default)
+    {
+        var query = Definitions.AsNoTracking();
+        if (!string.IsNullOrWhiteSpace(serviceName))
+            query = query.Where(d => d.Service.Name == serviceName);
+        if (!string.IsNullOrWhiteSpace(key))
+            query = query.Where(d => d.Key == key);
+        var entities = await query.OrderBy(d => d.Service.Name).ThenBy(d => d.Key).ToListAsync(ct);
+        return entities.Select(MapDefinition).ToList();
+    }
+
+    private async Task RequireServiceLanguageAsync(string serviceName, string code, CancellationToken ct)
+    {
+        if (!await db.ServiceLanguages.AnyAsync(l => l.Service.Name == serviceName && l.Code == code, ct))
+            throw new EmailTemplateWriteException("Language is not in this service's catalog. Add it in the service editor first.", false);
+    }
+
+    private async Task ValidateServiceLanguagesAsync(EmailTemplateDefinition definition, CancellationToken ct)
+    {
+        var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Name == definition.ServiceName
+                && (definition.ServiceId == Guid.Empty || s.Id == definition.ServiceId), ct)
+            ?? throw new EmailTemplateWriteException("Service does not exist. Create the service first.", false);
+        var codes = service.Languages.Select(l => l.Code).ToHashSet(StringComparer.Ordinal);
+        if (definition.Languages.Any(l => !codes.Contains(l.LanguageCode)))
+            throw new EmailTemplateWriteException("Language is not in this service's catalog. Add it in the service editor first.", false);
+    }
+
+    private Task<EmailTemplateDefinitionEntity?> FindDefinitionAsync(string serviceName, string key, CancellationToken ct) =>
+        Definitions.SingleOrDefaultAsync(d => d.Service.Name == serviceName && d.Key == key, ct);
+
+    private async Task<EmailTemplateDefinitionEntity> RequireDefinitionAsync(string serviceName, string key, CancellationToken ct) =>
+        await FindDefinitionAsync(serviceName, key, ct)
+        ?? throw new EmailTemplateWriteException("The template was removed. Reload the template list.");
+
+    private async Task<EmailTemplateDefinitionEntity> CreateDefinitionAsync(string serviceName, string key,
+        IReadOnlyList<EmailTemplateVariable> variables, CancellationToken ct)
+    {
+        var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Name == serviceName, ct)
+            ?? throw new EmailTemplateWriteException("Service does not exist. Create the service and its language codes first.", false);
+        var entity = new EmailTemplateDefinitionEntity
+        {
+            Service = service, Key = key, Variables = MapVariables(variables), Created = DateTimeOffset.UtcNow
+        };
+        db.TemplateDefinitions.Add(entity);
+        return entity;
+    }
+
+    private static void ValidateLegacy(EmailTemplate template)
+    {
+        EmailTemplateValidation.ValidateIdentity(template.ServiceName, template.Key);
+        EmailTemplateValidation.ValidateLanguage(template);
+        EmailTemplateValidation.ValidateVariables(template.Variables);
+    }
+
+    private static void EnsureMatchingContract(EmailTemplateDefinitionEntity definition, IReadOnlyList<EmailTemplateVariable> variables)
+    {
+        var shared = definition.Variables.Select(v => new EmailTemplateVariable { Name = v.Name, Required = v.Required }).ToList();
+        if (!EmailTemplateValidation.ContractsEqual(shared, variables))
+            throw new EmailTemplateWriteException("Variables conflict with the shared template contract. Edit shared variables in the template editor.");
+    }
+
+    private static void Touch(EmailTemplateDefinitionEntity definition)
+    {
+        definition.Revision = Guid.NewGuid();
+        definition.Updated = DateTimeOffset.UtcNow;
+    }
+
+    private static List<EmailTemplateVariableData> MapVariables(IReadOnlyList<EmailTemplateVariable> variables) =>
+        variables.Select(v => new EmailTemplateVariableData { Name = v.Name, Required = v.Required }).ToList();
+
+    private static EmailTemplateEntity NewLanguage(EmailTemplate model, EmailTemplateDefinitionEntity definition) => new()
+    {
+        Id = model.Id, Definition = definition, ServiceId = definition.Service.Id,
+        ServiceLanguage = definition.Service.Languages.SingleOrDefault(l => l.Code == model.LanguageCode)
+            ?? throw new EmailTemplateWriteException("Language is not in this service's catalog. Add it in the service editor first.", false),
+        Subject = model.Subject, HtmlBody = model.HtmlBody, TextBody = model.TextBody, Created = model.Created
     };
 
-    private static EmailTemplateEntity MapToEntity(EmailTemplate t) => new()
+    private static void SetContent(EmailTemplateEntity entity, EmailTemplate model)
     {
-        Id = t.Id,
+        entity.Subject = model.Subject;
-        ServiceName = t.ServiceName,
+        entity.HtmlBody = model.HtmlBody;
-        Key = t.Key,
+        entity.TextBody = model.TextBody;
-        LanguageCode = t.LanguageCode,
+        entity.Updated = DateTimeOffset.UtcNow;
-        Subject = t.Subject,
+    }
-        HtmlBody = t.HtmlBody,
+
-        TextBody = t.TextBody,
+    private static EmailTemplate MapLanguage(EmailTemplateEntity entity) => new()
-        Variables = t.Variables.Select(v => new EmailTemplateVariableData { Name = v.Name, Required = v.Required }).ToList(),
+    {
-        Created = t.Created,
+        Id = entity.Id, ServiceName = entity.Definition.Service.Name, Key = entity.Definition.Key,
-        Updated = t.Updated
+        LanguageCode = entity.ServiceLanguage.Code, Subject = entity.Subject, HtmlBody = entity.HtmlBody, TextBody = entity.TextBody,
+        Variables = entity.Definition.Variables.Select(v => new EmailTemplateVariable { Name = v.Name, Required = v.Required }).ToList(),
+        Created = entity.Created, Updated = entity.Updated
+    };
+
+    private static EmailTemplateDefinition MapDefinition(EmailTemplateDefinitionEntity entity) => new()
+    {
+        Id = entity.Id, ServiceId = entity.ServiceId, ServiceName = entity.Service.Name, Key = entity.Key, Revision = entity.Revision,
+        Variables = entity.Variables.Select(v => new EmailTemplateVariable { Name = v.Name, Required = v.Required }).ToList(),
+        Languages = entity.Languages.OrderBy(t => t.ServiceLanguage.Code).Select(MapLanguage).ToList(),
+        Created = entity.Created, Updated = entity.Updated
     };
 }

HrynCo.NotificationService.DAL.EF/Repositories/NotificationServiceRepository.cs

@@ -0,0 +1,215 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+
+namespace HrynCo.NotificationService.DAL.EF.Repositories;
+
+internal sealed class NotificationServiceRepository(NotificationDbContext db, TemplateMutationRunner mutations) : INotificationServiceRepository
+{
+    public async Task<IReadOnlyList<NotificationServiceInfo>> GetAllAsync(CancellationToken ct = default)
+    {
+        var services = await db.Services.AsNoTracking().Include(s => s.Languages).OrderBy(s => s.Name).ToListAsync(ct);
+        var counts = await VersionCountsAsync(ct);
+        return services.Select(s => Map(s, counts)).ToList();
+    }
+
+    public async Task<NotificationServiceInfo?> GetAsync(Guid id, CancellationToken ct = default)
+    {
+        var service = await db.Services.AsNoTracking().Include(s => s.Languages).SingleOrDefaultAsync(s => s.Id == id, ct);
+        return service is null ? null : Map(service, await VersionCountsAsync(ct));
+    }
+
+    public async Task<NotificationServiceInfo?> GetByNameAsync(string name, CancellationToken ct = default)
+    {
+        var service = await db.Services.AsNoTracking().Include(s => s.Languages).SingleOrDefaultAsync(s => s.Name == name, ct);
+        return service is null ? null : Map(service, await VersionCountsAsync(ct));
+    }
+
+    public async Task<bool> DeleteAsync(Guid id, Guid revision, CancellationToken ct = default)
+    {
+        var removed = false;
+        await mutations.ExecuteAsync(async () =>
+        {
+            if (revision == Guid.Empty)
+                throw new EmailTemplateWriteException("A nonempty service revision is required.", false);
+            var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Id == id, ct);
+            if (service is null)
+                return;
+            if (service.Revision != revision)
+                throw new EmailTemplateWriteException("The service revision changed. Read it again before deleting.");
+            if (await db.TemplateDefinitions.AnyAsync(d => d.ServiceId == id, ct))
+                throw new EmailTemplateWriteException("Remove every template definition before deleting this service, including definitions without translations.");
+            db.ServiceLanguages.RemoveRange(service.Languages);
+            db.Services.Remove(service);
+            removed = true;
+        }, ct);
+        return removed;
+    }
+
+    public Task SaveAsync(NotificationServiceInfo model, bool isNew, CancellationToken ct = default) => mutations.ExecuteAsync(async () =>
+    {
+        Validate(model);
+        var service = await LoadForSaveAsync(model, isNew, ct);
+        await ValidateLanguageChangesAsync(service, model, ct);
+        await StageLanguageCodeChangesAsync(service, model.Languages, ct);
+        service.Name = model.Name;
+        SynchronizeLanguages(service, model.Languages);
+        Touch(service);
+        await TouchDefinitionsAsync(service.Id, ct);
+        model.Id = service.Id;
+        model.Revision = service.Revision;
+    }, ct);
+
+    public Task RemoveLanguageAsync(Guid serviceId, Guid languageId, int expectedVersionCount, Guid expectedRevision, CancellationToken ct = default) =>
+        mutations.ExecuteAsync(async () =>
+        {
+            var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Id == serviceId, ct)
+                ?? throw new EmailTemplateWriteException("Service no longer exists. Reload services.");
+            var language = service.Languages.SingleOrDefault(l => l.Id == languageId)
+                ?? throw new EmailTemplateWriteException("Language no longer exists. Reload the service.");
+            var versions = await db.Templates.Where(t => t.ServiceLanguageId == languageId).ToListAsync(ct);
+            if (service.Revision != expectedRevision || versions.Count != expectedVersionCount)
+                throw new EmailTemplateWriteException("The service or affected version count changed. Review the current count and confirm again.");
+            db.Templates.RemoveRange(versions);
+            // Save dependent removals first because language deletion is restricted by its FK.
+            await db.SaveChangesAsync(ct);
+            db.ServiceLanguages.Remove(language);
+            Touch(service);
+            await TouchDefinitionsAsync(serviceId, ct);
+        }, ct);
+
+    private async Task<ServiceEntity> LoadForSaveAsync(NotificationServiceInfo model, bool isNew, CancellationToken ct)
+    {
+        if (await db.Services.AnyAsync(s => s.Name == model.Name && s.Id != model.Id, ct))
+            throw new EmailTemplateWriteException("A service with this name already exists.");
+        if (isNew)
+        {
+            var created = new ServiceEntity { Name = model.Name, Created = DateTimeOffset.UtcNow };
+            db.Services.Add(created);
+            return created;
+        }
+        var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Id == model.Id, ct);
+        if (service is null || service.Revision != model.Revision)
+            throw new EmailTemplateWriteException("This service changed after you opened it. Reload before saving.");
+        return service;
+    }
+
+    private async Task ValidateLanguageChangesAsync(ServiceEntity service, NotificationServiceInfo model, CancellationToken ct)
+    {
+        var ids = service.Languages.Select(l => l.Id).ToHashSet();
+        if (model.Languages.Any(l => l.Id != Guid.Empty && !ids.Contains(l.Id)))
+            throw new EmailTemplateWriteException("A language changed or was removed. Reload the service.");
+        ValidateChangedCodes(service, model.Languages);
+        var retained = model.Languages.Select(l => l.Id).ToHashSet();
+        var removed = service.Languages.Where(l => !retained.Contains(l.Id)).ToList();
+        foreach (var language in removed)
+        {
+            var count = await db.Templates.CountAsync(t => t.ServiceLanguageId == language.Id, ct);
+            if (count > 0)
+                throw new EmailTemplateWriteException($"Cannot remove language '{language.Code}': {count} version(s) use it. Use the separate delete-with-versions confirmation.");
+        }
+    }
+
+    private async Task StageLanguageCodeChangesAsync(ServiceEntity service, IReadOnlyList<ServiceLanguageInfo> languages, CancellationToken ct)
+    {
+        var requested = languages.Where(l => l.Id != Guid.Empty).ToDictionary(l => l.Id, l => l.Code);
+        var removed = service.Languages.Where(l => !requested.ContainsKey(l.Id)).ToList();
+        var changed = service.Languages.Where(l => requested.TryGetValue(l.Id, out var code) && code != l.Code).ToList();
+        if (removed.Count == 0 && changed.Count == 0)
+            return;
+        foreach (var language in removed)
+        {
+            db.ServiceLanguages.Remove(language);
+            service.Languages.Remove(language);
+        }
+        var reserved = service.Languages.Select(l => l.Code).Concat(languages.Select(l => l.Code)).ToHashSet(StringComparer.Ordinal);
+        foreach (var language in changed)
+            language.Code = TemporaryCode(reserved);
+        // Free old codes before final assignments, supporting swaps and replacing unused rows.
+        // These temporary identifiers remain invisible outside this transaction.
+        await db.SaveChangesAsync(ct);
+    }
+
+    private static string TemporaryCode(HashSet<string> reserved)
+    {
+        string code;
+        do { code = "~" + Guid.NewGuid().ToString("N")[..9]; }
+        while (!reserved.Add(code));
+        return code;
+    }
+
+    private void SynchronizeLanguages(ServiceEntity service, IReadOnlyList<ServiceLanguageInfo> languages)
+    {
+        var retained = languages.Select(l => l.Id).ToHashSet();
+        db.ServiceLanguages.RemoveRange(service.Languages.Where(l => !retained.Contains(l.Id)));
+        foreach (var model in languages)
+        {
+            var entity = service.Languages.SingleOrDefault(l => l.Id == model.Id);
+            if (entity is null)
+                db.ServiceLanguages.Add(new ServiceLanguageEntity { Service = service, Code = model.Code, Created = DateTimeOffset.UtcNow });
+            else
+                entity.Code = model.Code;
+        }
+    }
+
+    private async Task TouchDefinitionsAsync(Guid serviceId, CancellationToken ct)
+    {
+        var definitions = await db.TemplateDefinitions.Where(d => d.ServiceId == serviceId).ToListAsync(ct);
+        foreach (var definition in definitions)
+        {
+            definition.Revision = Guid.NewGuid();
+            definition.Updated = DateTimeOffset.UtcNow;
+        }
+    }
+
+    private Task<Dictionary<Guid, int>> VersionCountsAsync(CancellationToken ct) => db.Templates.AsNoTracking()
+        .GroupBy(t => t.ServiceLanguageId).Select(g => new { Id = g.Key, Count = g.Count() })
+        .ToDictionaryAsync(g => g.Id, g => g.Count, ct);
+
+    private static void Validate(NotificationServiceInfo service)
+    {
+        if (string.IsNullOrWhiteSpace(service.Name) || service.Name.Length > 100)
+            throw new EmailTemplateWriteException("Service name is required and must be at most 100 characters.", false);
+        foreach (var language in service.Languages)
+            ValidateCode(language.Code);
+        if (service.Languages.Select(l => l.Code).Distinct(StringComparer.Ordinal).Count() != service.Languages.Count)
+            throw new EmailTemplateWriteException("Language codes must be unique within the service.", false);
+        var ids = service.Languages.Where(l => l.Id != Guid.Empty).Select(l => l.Id).ToList();
+        if (ids.Distinct().Count() != ids.Count)
+            throw new EmailTemplateWriteException("Each service language can appear only once.", false);
+    }
+
+    private static void ValidateCode(string code)
+    {
+        if (string.IsNullOrWhiteSpace(code) || code.Length > 10)
+            throw new EmailTemplateWriteException("Language codes are required and must be at most 10 characters.", false);
+    }
+
+    private static void ValidateChangedCodes(ServiceEntity service, IReadOnlyList<ServiceLanguageInfo> languages)
+    {
+        var persisted = service.Languages.ToDictionary(l => l.Id, l => l.Code);
+        foreach (var language in languages)
+        {
+            if (persisted.TryGetValue(language.Id, out var original) && original == language.Code)
+                continue;
+            if (!System.Text.RegularExpressions.Regex.IsMatch(language.Code, "^[A-Za-z0-9]+(-[A-Za-z0-9]+)*$"))
+                throw new EmailTemplateWriteException("Use letters, numbers and hyphens in new or renamed language codes, without spaces. Codes are case-sensitive.", false);
+        }
+    }
+
+    private static void Touch(ServiceEntity service)
+    {
+        service.Revision = Guid.NewGuid();
+        service.Updated = DateTimeOffset.UtcNow;
+    }
+
+    private static NotificationServiceInfo Map(ServiceEntity service, IReadOnlyDictionary<Guid, int> counts) => new()
+    {
+        Id = service.Id, Name = service.Name, Revision = service.Revision,
+        Languages = service.Languages.OrderBy(l => l.Code).Select(l => new ServiceLanguageInfo
+        {
+            Id = l.Id, Code = l.Code, VersionCount = counts.GetValueOrDefault(l.Id)
+        }).ToList()
+    };
+}

HrynCo.NotificationService.DAL.EF/ServiceCollectionExtensions.cs

@@ -16,7 +16,10 @@ public static class ServiceCollectionExtensions
         services.AddDbContext<NotificationDbContext>(options =>
             options.UseNpgsql(connectionString));
 
+        services.AddScoped<TemplateMutationRunner>();
+        services.AddScoped<INotificationServiceRepository, NotificationServiceRepository>();
         services.AddScoped<IEmailTemplateRepository, EmailTemplateRepository>();
+        services.AddScoped<IEmailTemplateDefinitionRepository, EmailTemplateRepository>();
         services.AddScoped<IEmailChannelRepository, EmailChannelRepository>();
         services.AddScoped<IEmailChannelUsageRepository, EmailChannelUsageRepository>();
         services.AddScoped<IUnitOfWork, NotificationUnitOfWork>();

HrynCo.NotificationService.DAL.EF/TemplateMutationRunner.cs

@@ -0,0 +1,19 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace HrynCo.NotificationService.DAL.EF;
+
+internal sealed class TemplateMutationRunner(NotificationDbContext db)
+{
+    public async Task ExecuteAsync(Func<Task> write, CancellationToken ct)
+    {
+        await using var transaction = db.Database.CurrentTransaction is null
+            ? await db.Database.BeginTransactionAsync(ct) : null;
+        // Service/language administration and template writes share the same transaction lock.
+        // Counts, catalog membership and revision checks are therefore valid until commit.
+        await db.Database.ExecuteSqlRawAsync("SELECT pg_advisory_xact_lock(1601)", ct);
+        await write();
+        await db.SaveChangesAsync(ct);
+        if (transaction is not null)
+            await transaction.CommitAsync(ct);
+    }
+}

HrynCo.NotificationService.Migrator/DevelopmentDataSeeder.cs

@@ -0,0 +1,132 @@
+namespace HrynCo.NotificationService.Migrator;
+
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using Microsoft.Extensions.Logging;
+
+internal sealed class DevelopmentDataSeeder
+{
+    internal const string DefaultServiceName = "TestService";
+    internal const string DefaultLanguageCode = "en";
+
+    private readonly IEmailChannelRepository _channels;
+    private readonly IEmailTemplateRepository _templates;
+    private readonly INotificationServiceRepository _services;
+    private readonly ILogger<DevelopmentDataSeeder> _logger;
+
+    public DevelopmentDataSeeder(
+        IEmailChannelRepository channels,
+        IEmailTemplateRepository templates,
+        INotificationServiceRepository services,
+        ILogger<DevelopmentDataSeeder> logger)
+    {
+        _channels = channels;
+        _templates = templates;
+        _services = services;
+        _logger = logger;
+    }
+
+    public async Task SeedAsync(string serviceName, CancellationToken cancellationToken = default)
+    {
+        if (string.IsNullOrWhiteSpace(serviceName))
+            throw new InvalidOperationException("Development seed service name is not configured.");
+
+        await SeedMailpitChannelAsync(serviceName, cancellationToken);
+        await SeedServiceAsync(serviceName, cancellationToken);
+
+        foreach (EmailTemplate template in CreateTemplates(serviceName))
+        {
+            EmailTemplate? existing = await _templates.GetAsync(
+                template.ServiceName, template.Key, template.LanguageCode, cancellationToken);
+
+            if (existing is not null)
+            {
+                _logger.LogInformation(
+                    "Development email template already exists; leaving it unchanged [ServiceName={ServiceName}, Key={TemplateKey}, LanguageCode={LanguageCode}]",
+                    template.ServiceName, template.Key, template.LanguageCode);
+                continue;
+            }
+
+            await _templates.AddAsync(template, cancellationToken);
+            _logger.LogInformation(
+                "Created development email template [ServiceName={ServiceName}, Key={TemplateKey}, LanguageCode={LanguageCode}]",
+                template.ServiceName, template.Key, template.LanguageCode);
+        }
+    }
+
+    private async Task SeedServiceAsync(string serviceName, CancellationToken ct)
+    {
+        var services = await _services.GetAllAsync(ct);
+        var service = services.SingleOrDefault(s => s.Name == serviceName);
+        if (service?.Languages.Any(l => l.Code == DefaultLanguageCode) == true)
+            return;
+        var isNew = service is null;
+        service ??= new NotificationServiceInfo { Name = serviceName };
+        service.Languages = [..service.Languages, new ServiceLanguageInfo { Code = DefaultLanguageCode }];
+        await _services.SaveAsync(service, isNew, ct);
+    }
+
+    private async Task SeedMailpitChannelAsync(string serviceName, CancellationToken cancellationToken)
+    {
+        IReadOnlyList<EmailChannel> existingChannels = await _channels.GetByServiceAsync(
+            serviceName, cancellationToken);
+
+        if (existingChannels.Count > 0)
+        {
+            _logger.LogInformation(
+                "Development email channel already exists; leaving all channels unchanged [ServiceName={ServiceName}]",
+                serviceName);
+            return;
+        }
+
+        var channel = new EmailChannel
+        {
+            ServiceName = serviceName,
+            Priority = 1,
+            EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "mailpit",
+                Port = 1025,
+                Username = string.Empty,
+                Password = string.Empty,
+                UseSsl = false,
+                FromEmail = "no-reply@local.hrynco.test",
+                FromName = "HrynCo Development"
+            },
+            WarnThresholdPercent = 90,
+            IsActive = true,
+            Created = DateTimeOffset.UtcNow
+        };
+
+        await _channels.AddAsync(channel, cancellationToken);
+        _logger.LogInformation(
+            "Created Mailpit development email channel [ServiceName={ServiceName}]",
+            serviceName);
+    }
+
+    private static IReadOnlyList<EmailTemplate> CreateTemplates(string serviceName)
+    {
+        DateTimeOffset created = DateTimeOffset.UtcNow;
+
+        return
+        [
+            new EmailTemplate
+            {
+                ServiceName = serviceName,
+                Key = "TestEmail",
+                LanguageCode = DefaultLanguageCode,
+                Subject = "Test notification",
+                HtmlBody = "<p>Hello {{RecipientName}},</p><p>{{Message}}</p>",
+                TextBody = "Hello {{RecipientName}}, {{Message}}",
+                Variables =
+                [
+                    new EmailTemplateVariable { Name = "RecipientName", Required = true },
+                    new EmailTemplateVariable { Name = "Message", Required = true }
+                ],
+                Created = created
+            }
+        ];
+    }
+}

HrynCo.NotificationService.Migrator/Program.cs

@@ -1,5 +1,7 @@
-using HrynCo.NotificationService.DAL.EF;
+using HrynCo.NotificationService.DAL.EF;
+using HrynCo.NotificationService.Migrator;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Serilog;
@@ -21,8 +23,8 @@ try
             var connectionString = ctx.Configuration["App:ConnectionString"]
                 ?? throw new InvalidOperationException("App:ConnectionString is not configured.");
 
-            services.AddDbContext<NotificationDbContext>(options =>
+            services.AddNotificationDataAccess(connectionString);
-                options.UseNpgsql(connectionString));
+            services.AddScoped<DevelopmentDataSeeder>();
         })
         .Build();
 
@@ -32,6 +34,18 @@ try
     Log.Information("Applying migrations...");
     await db.Database.MigrateAsync();
     Log.Information("Migrations applied successfully.");
+
+    var environment = scope.ServiceProvider.GetRequiredService<IHostEnvironment>();
+    if (environment.IsDevelopment())
+    {
+        string serviceName = host.Services.GetRequiredService<IConfiguration>()["DevelopmentSeed:ServiceName"]
+                             ?? DevelopmentDataSeeder.DefaultServiceName;
+
+        Log.Information("Seeding development email configuration...");
+        var seeder = scope.ServiceProvider.GetRequiredService<DevelopmentDataSeeder>();
+        await seeder.SeedAsync(serviceName);
+        Log.Information("Development email configuration is ready.");
+    }
 }
 catch (Exception ex)
 {

HrynCo.NotificationService.Migrator/Properties/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("HrynCo.NotificationService.Services.Tests")]

HrynCo.NotificationService.Services.Tests/DevelopmentDataSeederTests.cs

@@ -0,0 +1,85 @@
+namespace HrynCo.NotificationService.Services.Tests;
+
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Migrator;
+using Microsoft.Extensions.Logging.Abstractions;
+using NSubstitute;
+
+public sealed class DevelopmentDataSeederTests
+{
+    private readonly IEmailChannelRepository _channels = Substitute.For<IEmailChannelRepository>();
+    private readonly IEmailTemplateRepository _templates = Substitute.For<IEmailTemplateRepository>();
+    private readonly INotificationServiceRepository _services = Substitute.For<INotificationServiceRepository>();
+
+    [Fact]
+    public async Task SeedAsync_WhenConfigurationIsMissing_CreatesMailpitChannelAndTestTemplate()
+    {
+        _channels.GetByServiceAsync("TestService", Arg.Any<CancellationToken>())
+            .Returns(Array.Empty<EmailChannel>());
+        _templates.GetAsync("TestService", "TestEmail", "en", Arg.Any<CancellationToken>())
+            .Returns((EmailTemplate?)null);
+
+        DevelopmentDataSeeder seeder = CreateSeeder();
+
+        await seeder.SeedAsync("TestService", CancellationToken.None);
+
+        await _channels.Received(1).AddAsync(
+            Arg.Is<EmailChannel>(channel => IsMailpitChannel(channel)),
+            Arg.Any<CancellationToken>());
+        await _templates.Received(1).AddAsync(
+            Arg.Is<EmailTemplate>(template =>
+                template.ServiceName == "TestService" &&
+                template.Key == "TestEmail" &&
+                template.Variables.Any(variable => variable.Name == "Message" && variable.Required)),
+            Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task SeedAsync_WhenConfigurationExists_DoesNotDuplicateOrOverwriteIt()
+    {
+        _channels.GetByServiceAsync("TestService", Arg.Any<CancellationToken>())
+            .Returns([new EmailChannel
+            {
+                ServiceName = "TestService",
+                EmailChannelType = EmailChannelType.Smtp,
+                Settings = new SmtpChannelSettings()
+            }]);
+        _templates.GetAsync("TestService", "TestEmail", "en", Arg.Any<CancellationToken>())
+            .Returns(new EmailTemplate
+            {
+                ServiceName = "TestService",
+                Key = "TestEmail",
+                LanguageCode = "en",
+                Subject = "Existing",
+                HtmlBody = "Existing",
+                TextBody = "Existing"
+            });
+
+        DevelopmentDataSeeder seeder = CreateSeeder();
+
+        await seeder.SeedAsync("TestService", CancellationToken.None);
+
+        await _channels.DidNotReceive().AddAsync(Arg.Any<EmailChannel>(), Arg.Any<CancellationToken>());
+        await _templates.DidNotReceive().AddAsync(Arg.Any<EmailTemplate>(), Arg.Any<CancellationToken>());
+        await _channels.DidNotReceive().UpdateAsync(Arg.Any<EmailChannel>(), Arg.Any<CancellationToken>());
+        await _templates.DidNotReceive().UpdateAsync(Arg.Any<EmailTemplate>(), Arg.Any<CancellationToken>());
+    }
+
+    private DevelopmentDataSeeder CreateSeeder() => new(
+        _channels,
+        _templates,
+        _services,
+        NullLogger<DevelopmentDataSeeder>.Instance);
+
+    private static bool IsMailpitChannel(EmailChannel channel)
+    {
+        return channel.ServiceName == "TestService" &&
+               channel.IsActive &&
+               channel.Settings is SmtpChannelSettings smtp &&
+               smtp.Host == "mailpit" &&
+               smtp.Port == 1025 &&
+               !smtp.UseSsl;
+    }
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/EmailTemplateRenderingServiceTests.cs

@@ -0,0 +1,88 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+
+public sealed class EmailTemplateRenderingServiceTests
+{
+    private readonly EmailTemplateRenderingService _service = new();
+
+    [Fact]
+    public void Render_InterpolatesItemTrackerVariables()
+    {
+        EmailTemplate template = CreateTemplate();
+        SendEmailMessageData data = CreateData(new Dictionary<string, string>
+        {
+            ["AppName"] = "StoreMate",
+            ["VerificationUrl"] = "https://example.invalid/verify"
+        });
+
+        RenderedEmail result = _service.Render(template, data);
+
+        Assert.Equal("Verify StoreMate", result.Subject);
+        Assert.Equal("<a href=\"https://example.invalid/verify\">Verify</a>", result.HtmlBody);
+        Assert.Equal("Verify at https://example.invalid/verify", result.TextBody);
+    }
+
+    [Fact]
+    public void Render_WhenRequiredVariableIsMissing_ThrowsObservableFailure()
+    {
+        EmailTemplate template = CreateTemplate();
+        SendEmailMessageData data = CreateData(new Dictionary<string, string>
+        {
+            ["AppName"] = "StoreMate"
+        });
+
+        InvalidDataException exception = Assert.Throws<InvalidDataException>(
+            () => _service.Render(template, data));
+
+        Assert.Equal("Required template variables are missing: VerificationUrl.", exception.Message);
+    }
+
+    [Fact]
+    public void Render_HtmlEncodesVariablesWithoutChangingSubjectOrTextBody()
+    {
+        EmailTemplate template = CreateTemplate();
+        SendEmailMessageData data = CreateData(new Dictionary<string, string>
+        {
+            ["AppName"] = "Invemory <script>alert('xss')</script>",
+            ["VerificationUrl"] = "https://example.invalid/verify?next=\" onclick=\"alert('xss')"
+        });
+
+        RenderedEmail result = _service.Render(template, data);
+
+        Assert.Equal("Verify Invemory <script>alert('xss')</script>", result.Subject);
+        Assert.Equal(
+            "<a href=\"https://example.invalid/verify?next=&quot; onclick=&quot;alert(&#39;xss&#39;)\">Verify</a>",
+            result.HtmlBody);
+        Assert.Equal(
+            "Verify at https://example.invalid/verify?next=\" onclick=\"alert('xss')",
+            result.TextBody);
+    }
+
+    private static EmailTemplate CreateTemplate() => new()
+    {
+        ServiceName = "StoreMate-Prod",
+        Key = "EmailVerification",
+        LanguageCode = "uk",
+        Subject = "Verify {{AppName}}",
+        HtmlBody = "<a href=\"{{VerificationUrl}}\">Verify</a>",
+        TextBody = "Verify at {{VerificationUrl}}",
+        Variables =
+        [
+            new EmailTemplateVariable { Name = "AppName", Required = true },
+            new EmailTemplateVariable { Name = "VerificationUrl", Required = true }
+        ]
+    };
+
+    private static SendEmailMessageData CreateData(IReadOnlyDictionary<string, string> variables) => new()
+    {
+        ServiceName = "StoreMate-Prod",
+        TemplateKey = "EmailVerification",
+        RecipientEmail = "owner@example.com",
+        RecipientName = "Owner",
+        LanguageCode = "uk",
+        Variables = variables
+    };
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/EmailTemplateServiceTests.cs

@@ -0,0 +1,97 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+using NSubstitute;
+
+public sealed class EmailTemplateServiceTests
+{
+    [Theory]
+    [InlineData("RU")]
+    [InlineData(" ru ")]
+    [InlineData(" RU ")]
+    public async Task GetAsync_WhenExactVersionIsMissing_RetriesLegacyTrimmedLowercaseCode(string requestedCode)
+    {
+        IEmailTemplateRepository repository = Substitute.For<IEmailTemplateRepository>();
+        var expected = Template("ru");
+        repository.GetAsync("TestService", "Welcome", "ru", Arg.Any<CancellationToken>()).Returns(expected);
+        var service = new EmailTemplateService(repository);
+
+        Assert.Same(expected, await service.GetAsync("TestService", "Welcome", requestedCode, default));
+        Assert.Equal(new[] { requestedCode, "ru" }, RequestedCodes(repository));
+    }
+
+    [Fact]
+    public async Task GetAsync_WhenBothExactAndLowercaseVersionsExist_PrefersExactVersion()
+    {
+        IEmailTemplateRepository repository = Substitute.For<IEmailTemplateRepository>();
+        var expected = Template("RU");
+        repository.GetAsync("TestService", "Welcome", "RU", Arg.Any<CancellationToken>()).Returns(expected);
+        repository.GetAsync("TestService", "Welcome", "ru", Arg.Any<CancellationToken>()).Returns(Template("ru"));
+        var service = new EmailTemplateService(repository);
+
+        Assert.Same(expected, await service.GetAsync("TestService", "Welcome", "RU", default));
+        Assert.Equal(new[] { "RU" }, RequestedCodes(repository));
+    }
+
+    [Fact]
+    public async Task GetAsync_WhenExactRegionalVersionExists_DoesNotNormalizeIt()
+    {
+        IEmailTemplateRepository repository = Substitute.For<IEmailTemplateRepository>();
+        var expected = Template("ru-RU");
+        repository.GetAsync("TestService", "Welcome", "ru-RU", Arg.Any<CancellationToken>()).Returns(expected);
+        var service = new EmailTemplateService(repository);
+
+        Assert.Same(expected, await service.GetAsync("TestService", "Welcome", "ru-RU", default));
+        Assert.Equal(new[] { "ru-RU" }, RequestedCodes(repository));
+    }
+
+    [Fact]
+    public async Task GetAsync_WhenMissingCodeIsAlreadyCanonical_QueriesOnlyOnce()
+    {
+        IEmailTemplateRepository repository = Substitute.For<IEmailTemplateRepository>();
+        var service = new EmailTemplateService(repository);
+
+        var error = await Assert.ThrowsAsync<InvalidOperationException>(() => service.GetAsync("TestService", "Welcome", "zz", default));
+
+        Assert.Contains("language='zz'", error.Message);
+        Assert.Equal(new[] { "zz" }, RequestedCodes(repository));
+    }
+
+    [Fact]
+    public async Task GetAsync_WhenRegionalLookupMisses_DoesNotScanOtherCaseOrRegionalVariants()
+    {
+        IEmailTemplateRepository repository = Substitute.For<IEmailTemplateRepository>();
+        repository.GetAsync("TestService", "Welcome", "ru-RU", Arg.Any<CancellationToken>()).Returns(Template("ru-RU"));
+        repository.GetAsync("TestService", "Welcome", "ru", Arg.Any<CancellationToken>()).Returns(Template("ru"));
+        var service = new EmailTemplateService(repository);
+
+        await Assert.ThrowsAsync<InvalidOperationException>(() => service.GetAsync("TestService", "Welcome", "RU-ru", default));
+
+        Assert.Equal(new[] { "RU-ru", "ru-ru" }, RequestedCodes(repository));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    public async Task GetAsync_WhenCodeIsBlank_RejectsBeforeRepositoryLookup(string? code)
+    {
+        IEmailTemplateRepository repository = Substitute.For<IEmailTemplateRepository>();
+        var service = new EmailTemplateService(repository);
+
+        await Assert.ThrowsAsync<InvalidDataException>(() => service.GetAsync("TestService", "Welcome", code, default));
+
+        Assert.Empty(repository.ReceivedCalls());
+    }
+
+    private static EmailTemplate Template(string code) => new()
+    {
+        ServiceName = "TestService", Key = "Welcome", LanguageCode = code, Subject = "Subject " + code,
+        HtmlBody = "<p>Hello</p>", TextBody = "Hello"
+    };
+
+    private static string[] RequestedCodes(IEmailTemplateRepository repository) => repository.ReceivedCalls()
+        .Select(call => (string)call.GetArguments()[2]!).ToArray();
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/NotificationDeliveryErrorFormatterTests.cs

@@ -0,0 +1,58 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+using System.Net.Mail;
+using System.Net.Sockets;
+
+public sealed class NotificationDeliveryErrorFormatterTests
+{
+    [Fact]
+    public void Format_UsesInnermostMessageAndRemovesLineBreaks()
+    {
+        var exception = new InvalidOperationException(
+            "outer",
+            new Exception("provider failed\r\nretry rejected"));
+
+        string result = NotificationDeliveryErrorFormatter.Format(exception);
+
+        Assert.Equal(
+            "Notification delivery failed after all retry attempts (provider failed retry rejected).",
+            result);
+    }
+
+    [Fact]
+    public void Format_UnresolvedSmtpHost_AddsSafeChannelContext()
+    {
+        var socketException = new SocketException((int)SocketError.HostNotFound);
+        var exception = new SmtpException("Failure sending mail.", socketException);
+
+        string result = NotificationDeliveryErrorFormatter.Format(exception);
+
+        Assert.Equal(
+            $"SMTP delivery failed after all retry attempts: the configured SMTP server host could not be resolved ({socketException.Message}).",
+            result);
+    }
+
+    [Fact]
+    public void Format_RefusedSmtpConnection_AddsSafeChannelContext()
+    {
+        var socketException = new SocketException((int)SocketError.ConnectionRefused);
+        var exception = new SmtpException("Failure sending mail.", socketException);
+
+        string result = NotificationDeliveryErrorFormatter.Format(exception);
+
+        Assert.Equal(
+            $"SMTP delivery failed after all retry attempts: the configured SMTP server refused the connection ({socketException.Message}).",
+            result);
+    }
+
+    [Fact]
+    public void Format_LongError_IsBoundedToOutboxColumnLength()
+    {
+        var exception = new Exception(new string('x', 2100));
+
+        string result = NotificationDeliveryErrorFormatter.Format(exception);
+
+        Assert.Equal(2000, result.Length);
+    }
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/NotificationResultPublisherTests.cs

@@ -0,0 +1,107 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+using Hrynco.RabbitMq;
+using Microsoft.Extensions.Logging.Abstractions;
+using NSubstitute;
+
+public sealed class NotificationResultPublisherTests
+{
+    [Fact]
+    public async Task PublishAsync_TerminalFailure_PublishesNeutralFailureResultToReplyQueue()
+    {
+        IRabbitMqPublisher rabbitMqPublisher = Substitute.For<IRabbitMqPublisher>();
+        var publisher = new NotificationResultPublisher(
+            rabbitMqPublisher,
+            NullLogger<NotificationResultPublisher>.Instance);
+        SendEmailMessage message = CreateMessage();
+        NotificationResultMessage? publishedResult = null;
+        rabbitMqPublisher
+            .When(x => x.PublishAsync(
+                "item-tracker.notifications.result",
+                Arg.Any<NotificationResultMessage>(),
+                Arg.Any<CancellationToken>()))
+            .Do(call => publishedResult = call.ArgAt<NotificationResultMessage>(1));
+
+        await publisher.PublishAsync(
+            message,
+            "Email provider could not deliver the notification.",
+            CancellationToken.None);
+
+        await rabbitMqPublisher.Received(1).PublishAsync(
+            "item-tracker.notifications.result",
+            Arg.Any<NotificationResultMessage>(),
+            CancellationToken.None);
+        Assert.NotNull(publishedResult);
+        Assert.Equal(message.CorrelationContext.CorrelationId, publishedResult.CorrelationContext.CorrelationId);
+        Assert.Null(publishedResult.CorrelationContext.ReplyTo);
+        Assert.Equal(message.Data.ServiceName, publishedResult.Data.ServiceName);
+        Assert.Equal(message.Data.TemplateKey, publishedResult.Data.TemplateKey);
+        Assert.Equal(message.Data.RecipientEmail, publishedResult.Data.RecipientEmail);
+        Assert.Equal("Email provider could not deliver the notification.", publishedResult.Data.ErrorMessage);
+        Assert.False(publishedResult.Data.IsSuccess);
+    }
+
+    [Fact]
+    public async Task PublishAsync_NoReplyQueue_DoesNotPublish()
+    {
+        IRabbitMqPublisher rabbitMqPublisher = Substitute.For<IRabbitMqPublisher>();
+        var publisher = new NotificationResultPublisher(
+            rabbitMqPublisher,
+            NullLogger<NotificationResultPublisher>.Instance);
+        SendEmailMessage message = CreateMessage();
+        message.CorrelationContext = message.CorrelationContext with { ReplyTo = null };
+
+        await publisher.PublishAsync(message, "delivery failed", CancellationToken.None);
+
+        await rabbitMqPublisher.DidNotReceive()
+            .PublishAsync<NotificationResultData>(
+                Arg.Any<string>(),
+                Arg.Any<NotificationResultMessage>(),
+                Arg.Any<CancellationToken>());
+    }
+
+    [Fact]
+    public async Task PublishAsync_ResultBrokerFailure_IsBestEffort()
+    {
+        IRabbitMqPublisher rabbitMqPublisher = Substitute.For<IRabbitMqPublisher>();
+        rabbitMqPublisher
+            .PublishAsync(
+                Arg.Any<string>(),
+                Arg.Any<NotificationResultMessage>(),
+                Arg.Any<CancellationToken>())
+            .Returns<Task>(_ => throw new InvalidOperationException("reply broker unavailable"));
+        var publisher = new NotificationResultPublisher(
+            rabbitMqPublisher,
+            NullLogger<NotificationResultPublisher>.Instance);
+
+        Exception? exception = await Record.ExceptionAsync(() => publisher.PublishAsync(
+            CreateMessage(),
+            "delivery failed",
+            CancellationToken.None));
+
+        Assert.Null(exception);
+    }
+
+    private static SendEmailMessage CreateMessage()
+    {
+        return new SendEmailMessage
+        {
+            CorrelationContext = new CorrelationContext
+            {
+                CorrelationId = "correlation-id",
+                ReplyTo = "item-tracker.notifications.result"
+            },
+            Data = new SendEmailMessageData
+            {
+                ServiceName = "TestService",
+                TemplateKey = "TestEmail",
+                RecipientEmail = "test.user@itemtracker.local",
+                RecipientName = "Test User",
+                LanguageCode = "en",
+                Variables = new Dictionary<string, string>()
+            }
+        };
+    }
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/RecipientAddressRedactorTests.cs

@@ -0,0 +1,16 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+
+public sealed class RecipientAddressRedactorTests
+{
+    [Theory]
+    [InlineData("owner@example.com", "o***@e***.com")]
+    [InlineData("a@b.test", "a***@b***.test")]
+    [InlineData("invalid", "***")]
+    [InlineData(null, "<missing>")]
+    public void Redact_DoesNotExposeFullAddress(string? address, string expected)
+    {
+        Assert.Equal(expected, RecipientAddressRedactor.Redact(address));
+    }
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/SendEmailContractTests.cs

@@ -0,0 +1,60 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using System.Text.Json;
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+
+public sealed class SendEmailContractTests
+{
+    private const string ItemTrackerPayload = """
+        {
+          "CorrelationContext": {
+            "CorrelationId": "3ec4ad3f-0a8a-49f3-b31d-cdad5d1b95cc",
+            "ReplyTo": "item-tracker.notifications.result"
+          },
+          "Data": {
+            "ServiceName": "StoreMate-Prod",
+            "TemplateKey": "EmailVerification",
+            "RecipientEmail": "owner@example.com",
+            "RecipientName": "StoreMate Owner",
+            "Variables": {
+              "AppName": "StoreMate",
+              "VerificationUrl": "https://example.invalid/sensitive-token"
+            },
+            "LanguageCode": "uk"
+          }
+        }
+        """;
+
+    [Fact]
+    public void PascalCaseItemTrackerPayload_DeserializesWithoutLosingValues()
+    {
+        SendEmailMessage? message = JsonSerializer.Deserialize<SendEmailMessage>(ItemTrackerPayload);
+
+        Assert.NotNull(message);
+        SendEmailMessageValidator.Validate(message);
+        Assert.Equal("3ec4ad3f-0a8a-49f3-b31d-cdad5d1b95cc", message.CorrelationContext.CorrelationId);
+        Assert.Equal("item-tracker.notifications.result", message.CorrelationContext.ReplyTo);
+        Assert.Equal("StoreMate-Prod", message.Data.ServiceName);
+        Assert.Equal("EmailVerification", message.Data.TemplateKey);
+        Assert.Equal("owner@example.com", message.Data.RecipientEmail);
+        Assert.Equal("StoreMate Owner", message.Data.RecipientName);
+        Assert.Equal("uk", message.Data.LanguageCode);
+        Assert.Equal("StoreMate", message.Data.Variables["AppName"]);
+        Assert.Equal(
+            "https://example.invalid/sensitive-token",
+            message.Data.Variables["VerificationUrl"]);
+    }
+
+    [Fact]
+    public void MissingLanguageCode_IsRejected()
+    {
+        SendEmailMessage? message = JsonSerializer.Deserialize<SendEmailMessage>(
+            ItemTrackerPayload.Replace("\"uk\"", "null", StringComparison.Ordinal));
+
+        InvalidDataException exception = Assert.Throws<InvalidDataException>(
+            () => SendEmailMessageValidator.Validate(message!));
+
+        Assert.Equal("LanguageCode is required.", exception.Message);
+    }
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/SendEmailDeliveryValidatorTests.cs

@@ -0,0 +1,77 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.Worker;
+using Hrynco.RabbitMq;
+
+public sealed class SendEmailDeliveryValidatorTests
+{
+    [Fact]
+    public void ValidItemTrackerDelivery_IsAccepted()
+    {
+        string? error = SendEmailDeliveryValidator.GetValidationError(
+            CreateMessage(),
+            CreateContext(),
+            SendEmailConsumer.SupportedMessageType);
+
+        Assert.Null(error);
+    }
+
+    [Fact]
+    public void MissingMessageId_IsRejected()
+    {
+        RabbitMqMessageContext context = CreateContext() with { MessageId = null };
+
+        string? error = SendEmailDeliveryValidator.GetValidationError(
+            CreateMessage(),
+            context,
+            SendEmailConsumer.SupportedMessageType);
+
+        Assert.Equal("AMQP MessageId is required.", error);
+    }
+
+    [Fact]
+    public void UnsupportedContractVersion_IsRejected()
+    {
+        RabbitMqMessageContext context = CreateContext() with
+        {
+            MessageType = "Notification.SendEmail.v2"
+        };
+
+        string? error = SendEmailDeliveryValidator.GetValidationError(
+            CreateMessage(),
+            context,
+            SendEmailConsumer.SupportedMessageType);
+
+        Assert.Equal("Unsupported AMQP message type 'Notification.SendEmail.v2'.", error);
+    }
+
+    private static RabbitMqMessageContext CreateContext() => new()
+    {
+        QueueName = SendEmailConsumer.IncomingQueue,
+        Exchange = string.Empty,
+        RoutingKey = SendEmailConsumer.IncomingQueue,
+        MessageId = Guid.NewGuid().ToString("D"),
+        MessageType = SendEmailConsumer.SupportedMessageType,
+        CorrelationId = "correlation-id",
+        ContentType = "application/json"
+    };
+
+    private static SendEmailMessage CreateMessage() => new()
+    {
+        CorrelationContext = new CorrelationContext
+        {
+            CorrelationId = "correlation-id",
+            ReplyTo = "item-tracker.notifications.result"
+        },
+        Data = new SendEmailMessageData
+        {
+            ServiceName = "StoreMate-Prod",
+            TemplateKey = "EmailVerification",
+            RecipientEmail = "owner@example.com",
+            RecipientName = "Owner",
+            LanguageCode = "uk",
+            Variables = new Dictionary<string, string> { ["AppName"] = "StoreMate" }
+        }
+    };
+}

HrynCo.NotificationService.Services.Tests/EmailProcessing/SendEmailServiceTests.cs

@@ -0,0 +1,123 @@
+namespace HrynCo.NotificationService.Services.Tests.EmailProcessing;
+
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+using Hrynco.RabbitMq;
+using Microsoft.Extensions.Logging.Abstractions;
+using NSubstitute;
+
+public sealed class SendEmailServiceTests
+{
+    [Fact]
+    public async Task ProcessAsync_ValidItemTrackerMessage_SendsOnceAndUpdatesUsage()
+    {
+        Guid channelId = Guid.NewGuid();
+        var settings = new SmtpChannelSettings
+        {
+            Host = "smtp.example.invalid",
+            Port = 587,
+            Username = "smtp-user",
+            Password = "not-a-real-secret",
+            UseSsl = true,
+            FromEmail = "notifications@example.com",
+            FromName = "StoreMate"
+        };
+        var channel = new EmailChannel
+        {
+            Id = channelId,
+            ServiceName = "StoreMate-Prod",
+            Priority = 1,
+            EmailChannelType = EmailChannelType.Smtp,
+            Settings = settings,
+            IsActive = true
+        };
+        var template = new EmailTemplate
+        {
+            ServiceName = "StoreMate-Prod",
+            Key = "EmailVerification",
+            LanguageCode = "uk",
+            Subject = "Verify {{AppName}}",
+            HtmlBody = "<p>{{AppName}}</p>",
+            TextBody = "{{AppName}}",
+            Variables = [new EmailTemplateVariable { Name = "AppName", Required = true }]
+        };
+
+        IEmailChannelRepository channels = Substitute.For<IEmailChannelRepository>();
+        channels.GetByServiceAsync("StoreMate-Prod", Arg.Any<CancellationToken>())
+            .Returns([channel]);
+        IEmailChannelUsageRepository usage = Substitute.For<IEmailChannelUsageRepository>();
+        IEmailTemplateService templates = Substitute.For<IEmailTemplateService>();
+        templates.GetAsync("StoreMate-Prod", "EmailVerification", "uk", Arg.Any<CancellationToken>())
+            .Returns(template);
+        var renderer = new EmailTemplateRenderingService();
+        var smtp = new RecordingSmtpEmailSender();
+        INotificationResultPublisher resultPublisher = Substitute.For<INotificationResultPublisher>();
+        var service = new SendEmailService(
+            channels,
+            usage,
+            templates,
+            renderer,
+            smtp,
+            resultPublisher,
+            NullLogger<SendEmailService>.Instance);
+        var message = new SendEmailMessage
+        {
+            CorrelationContext = new CorrelationContext
+            {
+                CorrelationId = Guid.NewGuid().ToString("D")
+            },
+            Data = new SendEmailMessageData
+            {
+                ServiceName = "StoreMate-Prod",
+                TemplateKey = "EmailVerification",
+                RecipientEmail = "owner@example.com",
+                RecipientName = "Owner",
+                LanguageCode = "uk",
+                Variables = new Dictionary<string, string> { ["AppName"] = "StoreMate" }
+            }
+        };
+
+        await service.ProcessAsync(message, CancellationToken.None);
+
+        Assert.Equal(1, smtp.SendCount);
+        Assert.Same(settings, smtp.Settings);
+        Assert.Equal("Verify StoreMate", smtp.Email?.Subject);
+        Assert.Equal("owner@example.com", smtp.RecipientEmail);
+        Assert.Equal("Owner", smtp.RecipientName);
+        await usage.Received(1).IncrementUsageAsync(
+            channelId,
+            Arg.Any<DateOnly>(),
+            CancellationToken.None);
+        await resultPublisher.Received(1).PublishAsync(
+            message,
+            null,
+            CancellationToken.None);
+    }
+
+    private sealed class RecordingSmtpEmailSender : ISmtpEmailSender
+    {
+        public int SendCount { get; private set; }
+        public SmtpChannelSettings? Settings { get; private set; }
+        public RenderedEmail? Email { get; private set; }
+        public string? RecipientEmail { get; private set; }
+        public string? RecipientName { get; private set; }
+
+        public Task SendAsync(
+            SmtpChannelSettings settings,
+            RenderedEmail email,
+            string recipientEmail,
+            string recipientName,
+            CancellationToken cancellationToken)
+        {
+            SendCount++;
+            Settings = settings;
+            Email = email;
+            RecipientEmail = recipientEmail;
+            RecipientName = recipientName;
+            return Task.CompletedTask;
+        }
+    }
+}

HrynCo.NotificationService.Services.Tests/HrynCo.NotificationService.Services.Tests.csproj

@@ -10,6 +10,7 @@
   <ItemGroup>
     <PackageReference Include="coverlet.collector" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="NSubstitute" />
     <PackageReference Include="xunit" />
     <PackageReference Include="xunit.runner.visualstudio" />
   </ItemGroup>
@@ -21,6 +22,10 @@
   <ItemGroup>
     <ProjectReference Include="..\HrynCo.NotificationService.Services\HrynCo.NotificationService.Services.csproj" />
     <ProjectReference Include="..\HrynCo.NotificationService.DAL.Abstract\HrynCo.NotificationService.DAL.Abstract.csproj" />
+    <ProjectReference Include="..\HrynCo.NotificationService.Contracts\HrynCo.NotificationService.Contracts.csproj" />
+    <ProjectReference Include="..\HrynCo.NotificationService.Worker.Services\HrynCo.NotificationService.Worker.Services.csproj" />
+    <ProjectReference Include="..\HrynCo.NotificationService.Worker\HrynCo.NotificationService.Worker.csproj" />
+    <ProjectReference Include="..\HrynCo.NotificationService.Migrator\HrynCo.NotificationService.Migrator.csproj" />
   </ItemGroup>
 
 </Project>

HrynCo.NotificationService.Services.Tests/UnitTest1.cs

@@ -1,10 +0,0 @@
-namespace HrynCo.NotificationService.Services.Tests;
-
-public class UnitTest1
-{
-    [Fact]
-    public void Test1()
-    {
-
-    }
-}

HrynCo.NotificationService.Services/EmailChannels/Send/SendEmailHandler.cs

@@ -1,5 +1,6 @@
 using System.Net;
 using System.Net.Mail;
+using System.Text;
 using HrynCo.NotificationService.DAL.Abstract.Providers;
 using HrynCo.NotificationService.DAL.Abstract.Repositories;
 using HrynCo.NotificationService.Services.Core;
@@ -48,14 +49,16 @@ internal sealed class SendEmailHandler
             {
                 From = new MailAddress(smtp.FromEmail, smtp.FromName),
                 Subject = request.Subject,
-                Body = request.HtmlBody,
+                Body = request.TextBody ?? string.Empty,
-                IsBodyHtml = true
+                IsBodyHtml = false,
+                BodyEncoding = Encoding.UTF8,
+                SubjectEncoding = Encoding.UTF8
             };
 
-            if (!string.IsNullOrWhiteSpace(request.TextBody))
+            if (!string.IsNullOrWhiteSpace(request.HtmlBody))
             {
-                var plain = AlternateView.CreateAlternateViewFromString(request.TextBody, null, "text/plain");
+                var html = AlternateView.CreateAlternateViewFromString(request.HtmlBody, Encoding.UTF8, "text/html");
-                mail.AlternateViews.Add(plain);
+                mail.AlternateViews.Add(html);
             }
 
             mail.To.Add(new MailAddress(request.RecipientEmail, request.RecipientName));

HrynCo.NotificationService.Services/EmailTemplates/Create/CreateEmailTemplateHandler.cs

@@ -39,7 +39,14 @@ internal sealed class CreateEmailTemplateHandler
             Variables = request.Variables
         };
 
+        try
+        {
             await _templates.AddAsync(template, cancellationToken);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Guid>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
 
         return Success(template.Id);
     }

HrynCo.NotificationService.Services/EmailTemplates/Delete/DeleteEmailTemplateCommand.cs

@@ -7,5 +7,6 @@ namespace HrynCo.NotificationService.Services.EmailTemplates.Delete;
 public sealed record DeleteEmailTemplateCommand(
     string ServiceName,
     string Key,
-    string LanguageCode
+    string LanguageCode,
+    Guid? ExpectedVersionId = null
 ) : IRequest<ServiceResult<Unit>>;

HrynCo.NotificationService.Services/EmailTemplates/Delete/DeleteEmailTemplateHandler.cs

@@ -1,3 +1,4 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
 using HrynCo.DAL.Abstract;
 using HrynCo.NotificationService.DAL.Abstract.Repositories;
 using HrynCo.NotificationService.Services.Core;
@@ -27,8 +28,17 @@ internal sealed class DeleteEmailTemplateHandler
 
         if (template is null)
             return Failure<Unit>("Template not found.", ServiceErrorCode.NotFound);
+        if (request.ExpectedVersionId is Guid expectedId && template.Id != expectedId)
+            return Failure<Unit>("Template changed after you opened it. Reload before deleting.", ServiceErrorCode.Conflict);
 
+        try
+        {
             await _templates.DeleteAsync(template, cancellationToken);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
 
         return Success(Unit.Value);
     }

HrynCo.NotificationService.Services/EmailTemplates/GetAll/GetAllEmailTemplatesHandler.cs

@@ -22,7 +22,7 @@ internal sealed class GetAllEmailTemplatesHandler
     protected override async Task<ServiceResult<IReadOnlyList<EmailTemplate>>> DoOnHandle(
         GetAllEmailTemplatesQuery request, CancellationToken cancellationToken)
     {
-        var templates = await _templates.GetAllAsync(cancellationToken);
+        var templates = await _templates.GetAllAsync(request.ServiceName, request.Key, cancellationToken);
         return Success(templates);
     }
 }

HrynCo.NotificationService.Services/EmailTemplates/GetAll/GetAllEmailTemplatesQuery.cs

@@ -4,4 +4,5 @@ using HrynCo.NotificationService.Services.Core;
 
 namespace HrynCo.NotificationService.Services.EmailTemplates.GetAll;
 
-public sealed record GetAllEmailTemplatesQuery : IRequest<ServiceResult<IReadOnlyList<EmailTemplate>>>;
+public sealed record GetAllEmailTemplatesQuery(string? ServiceName = null, string? Key = null)
+    : IRequest<ServiceResult<IReadOnlyList<EmailTemplate>>>;

HrynCo.NotificationService.Services/EmailTemplates/SaveDefinition/SaveEmailTemplateDefinitionCommand.cs

@@ -0,0 +1,8 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.EmailTemplates.SaveDefinition;
+
+public sealed record SaveEmailTemplateDefinitionCommand(EmailTemplateDefinition Definition, bool IsNew)
+    : IRequest<ServiceResult<Guid>>;

HrynCo.NotificationService.Services/EmailTemplates/SaveDefinition/SaveEmailTemplateDefinitionHandler.cs

@@ -0,0 +1,26 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.EmailTemplates.SaveDefinition;
+
+internal sealed class SaveEmailTemplateDefinitionHandler(
+    IContextualSerilogLogger<SaveEmailTemplateDefinitionCommand> logger,
+    IEmailTemplateDefinitionRepository definitions)
+    : RequestHandler<SaveEmailTemplateDefinitionCommand, ServiceResult<Guid>>(logger)
+{
+    protected override async Task<ServiceResult<Guid>> DoOnHandle(SaveEmailTemplateDefinitionCommand request, CancellationToken cancellationToken)
+    {
+        try
+        {
+            await definitions.SaveDefinitionAsync(request.Definition, request.IsNew, cancellationToken);
+            return Success(request.Definition.Id);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Guid>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Services/EmailTemplates/Update/UpdateEmailTemplateHandler.cs

@@ -1,3 +1,4 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
 using HrynCo.DAL.Abstract;
 using HrynCo.NotificationService.DAL.Abstract.Repositories;
 using HrynCo.NotificationService.Services.Core;
@@ -34,7 +35,14 @@ internal sealed class UpdateEmailTemplateHandler
         template.Variables = request.Variables;
         template.Updated = DateTimeOffset.UtcNow;
 
+        try
+        {
             await _templates.UpdateAsync(template, cancellationToken);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
 
         return Success(Unit.Value);
     }

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteEmailTemplateDefinitionCommand.cs

@@ -0,0 +1,7 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+using Unit = HrynCo.NotificationService.Services.Core.Unit;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record DeleteEmailTemplateDefinitionCommand(Guid ServiceId, string Key, Guid Revision) : IRequest<ServiceResult<Unit>>;

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteEmailTemplateDefinitionHandler.cs

@@ -0,0 +1,25 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class DeleteEmailTemplateDefinitionHandler(
+    IContextualSerilogLogger<DeleteEmailTemplateDefinitionCommand> logger, IEmailTemplateDefinitionRepository repository)
+    : RequestHandler<DeleteEmailTemplateDefinitionCommand, ServiceResult<Unit>>(logger)
+{
+    protected override async Task<ServiceResult<Unit>> DoOnHandle(DeleteEmailTemplateDefinitionCommand request, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var removed = await repository.DeleteDefinitionAsync(request.ServiceId, request.Key, request.Revision, cancellationToken);
+            return removed ? Success(Unit.Value) : Failure<Unit>("Template definition not found.", ServiceErrorCode.NotFound);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteNotificationServiceCommand.cs

@@ -0,0 +1,7 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+using Unit = HrynCo.NotificationService.Services.Core.Unit;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record DeleteNotificationServiceCommand(Guid ServiceId, Guid Revision) : IRequest<ServiceResult<Unit>>;

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteNotificationServiceHandler.cs

@@ -0,0 +1,25 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class DeleteNotificationServiceHandler(
+    IContextualSerilogLogger<DeleteNotificationServiceCommand> logger, INotificationServiceRepository repository)
+    : RequestHandler<DeleteNotificationServiceCommand, ServiceResult<Unit>>(logger)
+{
+    protected override async Task<ServiceResult<Unit>> DoOnHandle(DeleteNotificationServiceCommand request, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var removed = await repository.DeleteAsync(request.ServiceId, request.Revision, cancellationToken);
+            return removed ? Success(Unit.Value) : Failure<Unit>("Service not found.", ServiceErrorCode.NotFound);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteServiceLanguageVersionsCommand.cs

@@ -0,0 +1,7 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+using Unit = HrynCo.NotificationService.Services.Core.Unit;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record DeleteServiceLanguageVersionsCommand(Guid ServiceId, Guid LanguageId, Guid Revision, int ExpectedVersionCount, bool ConfirmDelete) : IRequest<ServiceResult<Unit>>;

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteServiceLanguageVersionsHandler.cs

@@ -0,0 +1,30 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class DeleteServiceLanguageVersionsHandler(
+    IContextualSerilogLogger<DeleteServiceLanguageVersionsCommand> logger, INotificationServiceRepository services)
+    : RequestHandler<DeleteServiceLanguageVersionsCommand, ServiceResult<Unit>>(logger)
+{
+    protected override async Task<ServiceResult<Unit>> DoOnHandle(DeleteServiceLanguageVersionsCommand request, CancellationToken cancellationToken)
+    {
+        if (!request.ConfirmDelete || request.ExpectedVersionCount < 0 || request.Revision == Guid.Empty)
+            return Failure<Unit>("ConfirmDelete must be true; a nonnegative expectedVersionCount and nonempty service revision are required.", ServiceErrorCode.InvalidRequest);
+        var service = await services.GetAsync(request.ServiceId, cancellationToken);
+        if (service?.Languages.Any(l => l.Id == request.LanguageId) != true)
+            return Failure<Unit>("Service language not found.", ServiceErrorCode.NotFound);
+        try
+        {
+            await services.RemoveLanguageAsync(request.ServiceId, request.LanguageId, request.ExpectedVersionCount, request.Revision, cancellationToken);
+            return Success(Unit.Value);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteUnusedServiceLanguageCommand.cs

@@ -0,0 +1,7 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+using Unit = HrynCo.NotificationService.Services.Core.Unit;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record DeleteUnusedServiceLanguageCommand(Guid ServiceId, Guid LanguageId, Guid Revision) : IRequest<ServiceResult<Unit>>;

HrynCo.NotificationService.Services/TemplateDefinitions/DeleteUnusedServiceLanguageHandler.cs

@@ -0,0 +1,34 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class DeleteUnusedServiceLanguageHandler(
+    IContextualSerilogLogger<DeleteUnusedServiceLanguageCommand> logger, INotificationServiceRepository services)
+    : RequestHandler<DeleteUnusedServiceLanguageCommand, ServiceResult<Unit>>(logger)
+{
+    protected override async Task<ServiceResult<Unit>> DoOnHandle(DeleteUnusedServiceLanguageCommand request, CancellationToken cancellationToken)
+    {
+        if (request.Revision == Guid.Empty)
+            return Failure<Unit>("A nonempty service revision is required.", ServiceErrorCode.InvalidRequest);
+        var service = await services.GetAsync(request.ServiceId, cancellationToken);
+        var language = service?.Languages.SingleOrDefault(l => l.Id == request.LanguageId);
+        if (language is null)
+            return Failure<Unit>("Service language not found.", ServiceErrorCode.NotFound);
+        if (language.VersionCount > 0)
+            return Failure<Unit>("This language has template versions. Use delete-with-versions with explicit confirmation and the current count.", ServiceErrorCode.Conflict);
+        try
+        {
+            // The repository repeats the zero-count and revision checks under its mutation lock.
+            await services.RemoveLanguageAsync(request.ServiceId, request.LanguageId, 0, request.Revision, cancellationToken);
+            return Success(Unit.Value);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/EmailTemplateDefinitionDto.cs

@@ -0,0 +1,5 @@
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record EmailTemplateDefinitionDto(Guid Id, Guid ServiceId, string ServiceName, string Key, Guid Revision,
+    IReadOnlyList<TemplateVariableDto> Variables, IReadOnlyList<TemplateTranslationDto> Translations,
+    DateTimeOffset Created, DateTimeOffset? Updated);

HrynCo.NotificationService.Services/TemplateDefinitions/GetAllNotificationServicesHandler.cs

@@ -0,0 +1,17 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class GetAllNotificationServicesHandler(
+    IContextualSerilogLogger<GetAllNotificationServicesQuery> logger, INotificationServiceRepository services)
+    : RequestHandler<GetAllNotificationServicesQuery, ServiceResult<IReadOnlyList<NotificationServiceDto>>>(logger)
+{
+    protected override async Task<ServiceResult<IReadOnlyList<NotificationServiceDto>>> DoOnHandle(GetAllNotificationServicesQuery request, CancellationToken cancellationToken)
+    {
+        var all = await services.GetAllAsync(cancellationToken);
+        return Success<IReadOnlyList<NotificationServiceDto>>(all.Select(NotificationServiceMapping.Map).ToList());
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/GetAllNotificationServicesQuery.cs

@@ -0,0 +1,6 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record GetAllNotificationServicesQuery() : IRequest<ServiceResult<IReadOnlyList<NotificationServiceDto>>>;

HrynCo.NotificationService.Services/TemplateDefinitions/GetEmailTemplateDefinitionHandler.cs

@@ -0,0 +1,19 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class GetEmailTemplateDefinitionHandler(
+    IContextualSerilogLogger<GetEmailTemplateDefinitionQuery> logger, IEmailTemplateDefinitionRepository definitions)
+    : RequestHandler<GetEmailTemplateDefinitionQuery, ServiceResult<EmailTemplateDefinitionDto>>(logger)
+{
+    protected override async Task<ServiceResult<EmailTemplateDefinitionDto>> DoOnHandle(GetEmailTemplateDefinitionQuery request, CancellationToken cancellationToken)
+    {
+        var definition = await definitions.GetDefinitionAsync(request.ServiceId, request.Key, cancellationToken);
+        return definition is null
+            ? Failure<EmailTemplateDefinitionDto>("Template definition not found.", ServiceErrorCode.NotFound)
+            : Success(TemplateDefinitionMapping.Map(definition));
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/GetEmailTemplateDefinitionQuery.cs

@@ -0,0 +1,6 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record GetEmailTemplateDefinitionQuery(Guid ServiceId, string Key) : IRequest<ServiceResult<EmailTemplateDefinitionDto>>;

HrynCo.NotificationService.Services/TemplateDefinitions/GetNotificationServiceHandler.cs

@@ -0,0 +1,23 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class GetNotificationServiceHandler(
+    IContextualSerilogLogger<GetNotificationServiceQuery> logger, INotificationServiceRepository services)
+    : RequestHandler<GetNotificationServiceQuery, ServiceResult<NotificationServiceDto>>(logger)
+{
+    protected override async Task<ServiceResult<NotificationServiceDto>> DoOnHandle(GetNotificationServiceQuery request, CancellationToken cancellationToken)
+    {
+        if (request.ServiceId is null && string.IsNullOrWhiteSpace(request.Name))
+            return Failure<NotificationServiceDto>("An exact service name is required.", ServiceErrorCode.InvalidRequest);
+        var service = request.ServiceId is Guid id
+            ? await services.GetAsync(id, cancellationToken)
+            : await services.GetByNameAsync(request.Name!, cancellationToken);
+        return service is null
+            ? Failure<NotificationServiceDto>("Service not found.", ServiceErrorCode.NotFound)
+            : Success(NotificationServiceMapping.Map(service));
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/GetNotificationServiceQuery.cs

@@ -0,0 +1,6 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record GetNotificationServiceQuery(Guid? ServiceId, string? Name) : IRequest<ServiceResult<NotificationServiceDto>>;

HrynCo.NotificationService.Services/TemplateDefinitions/GetServiceTemplateDefinitionsHandler.cs

@@ -0,0 +1,20 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class GetServiceTemplateDefinitionsHandler(
+    IContextualSerilogLogger<GetServiceTemplateDefinitionsQuery> logger,
+    INotificationServiceRepository services, IEmailTemplateDefinitionRepository definitions)
+    : RequestHandler<GetServiceTemplateDefinitionsQuery, ServiceResult<IReadOnlyList<EmailTemplateDefinitionDto>>>(logger)
+{
+    protected override async Task<ServiceResult<IReadOnlyList<EmailTemplateDefinitionDto>>> DoOnHandle(GetServiceTemplateDefinitionsQuery request, CancellationToken cancellationToken)
+    {
+        if (await services.GetAsync(request.ServiceId, cancellationToken) is null)
+            return Failure<IReadOnlyList<EmailTemplateDefinitionDto>>("Service not found.", ServiceErrorCode.NotFound);
+        var all = await definitions.GetDefinitionsAsync(request.ServiceId, cancellationToken);
+        return Success<IReadOnlyList<EmailTemplateDefinitionDto>>(all.Select(TemplateDefinitionMapping.Map).ToList());
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/GetServiceTemplateDefinitionsQuery.cs

@@ -0,0 +1,6 @@
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record GetServiceTemplateDefinitionsQuery(Guid ServiceId) : IRequest<ServiceResult<IReadOnlyList<EmailTemplateDefinitionDto>>>;

HrynCo.NotificationService.Services/TemplateDefinitions/NotificationServiceDto.cs

@@ -0,0 +1,3 @@
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record NotificationServiceDto(Guid Id, string Name, Guid Revision, IReadOnlyList<string> SupportedLanguageCodes, IReadOnlyList<ServiceLanguageDto> Languages);

HrynCo.NotificationService.Services/TemplateDefinitions/NotificationServiceMapping.cs

@@ -0,0 +1,10 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal static class NotificationServiceMapping
+{
+    public static NotificationServiceDto Map(NotificationServiceInfo service) =>
+        new(service.Id, service.Name, service.Revision, service.Languages.Select(l => l.Code).ToList(),
+            service.Languages.Select(l => new ServiceLanguageDto(l.Id, l.Code, l.VersionCount)).ToList());
+}

HrynCo.NotificationService.Services/TemplateDefinitions/SaveNotificationServiceCommand.cs

@@ -0,0 +1,7 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record SaveNotificationServiceCommand(NotificationServiceInfo Service, bool IsNew) : IRequest<ServiceResult<NotificationServiceDto>>;

HrynCo.NotificationService.Services/TemplateDefinitions/SaveNotificationServiceHandler.cs

@@ -0,0 +1,30 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class SaveNotificationServiceHandler(
+    IContextualSerilogLogger<SaveNotificationServiceCommand> logger, INotificationServiceRepository services)
+    : RequestHandler<SaveNotificationServiceCommand, ServiceResult<NotificationServiceDto>>(logger)
+{
+    protected override async Task<ServiceResult<NotificationServiceDto>> DoOnHandle(SaveNotificationServiceCommand request, CancellationToken cancellationToken)
+    {
+        if (!request.IsNew && request.Service.Revision == Guid.Empty)
+            return Failure<NotificationServiceDto>("A nonempty service revision is required for update.", ServiceErrorCode.InvalidRequest);
+        if (!request.IsNew && await services.GetAsync(request.Service.Id, cancellationToken) is null)
+            return Failure<NotificationServiceDto>("Service not found.", ServiceErrorCode.NotFound);
+        try
+        {
+            await services.SaveAsync(request.Service, request.IsNew, cancellationToken);
+            var saved = await services.GetAsync(request.Service.Id, cancellationToken);
+            return Success(NotificationServiceMapping.Map(saved!));
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<NotificationServiceDto>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Services/TemplateDefinitions/ServiceLanguageDto.cs

@@ -0,0 +1,3 @@
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record ServiceLanguageDto(Guid Id, string Code, int VersionCount);

HrynCo.NotificationService.Services/TemplateDefinitions/TemplateDefinitionMapping.cs

@@ -0,0 +1,12 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal static class TemplateDefinitionMapping
+{
+    public static EmailTemplateDefinitionDto Map(EmailTemplateDefinition definition) => new(
+        definition.Id, definition.ServiceId, definition.ServiceName, definition.Key, definition.Revision,
+        definition.Variables.Select(v => new TemplateVariableDto(v.Name, v.Required)).ToList(),
+        definition.Languages.Select(t => new TemplateTranslationDto(t.Id, t.LanguageCode, t.Subject, t.HtmlBody, t.TextBody, t.Created, t.Updated)).ToList(),
+        definition.Created, definition.Updated);
+}

HrynCo.NotificationService.Services/TemplateDefinitions/TemplateTranslationDto.cs

@@ -0,0 +1,3 @@
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record TemplateTranslationDto(Guid Id, string LanguageCode, string Subject, string HtmlBody, string TextBody, DateTimeOffset Created, DateTimeOffset? Updated);

HrynCo.NotificationService.Services/TemplateDefinitions/TemplateVariableDto.cs

@@ -0,0 +1,3 @@
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record TemplateVariableDto(string Name, bool Required);

HrynCo.NotificationService.Services/TemplateDefinitions/UpsertEmailTemplateDefinitionCommand.cs

@@ -0,0 +1,7 @@
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using MediatR;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+public sealed record UpsertEmailTemplateDefinitionCommand(EmailTemplateDefinitionPatch Patch) : IRequest<ServiceResult<EmailTemplateDefinitionDto>>;

HrynCo.NotificationService.Services/TemplateDefinitions/UpsertEmailTemplateDefinitionHandler.cs

@@ -0,0 +1,27 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using HrynCo.NotificationService.Services.Core;
+using HrynCo.NotificationService.Services.Logging;
+using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;
+
+namespace HrynCo.NotificationService.Services.TemplateDefinitions;
+
+internal sealed class UpsertEmailTemplateDefinitionHandler(
+    IContextualSerilogLogger<UpsertEmailTemplateDefinitionCommand> logger, IEmailTemplateDefinitionRepository definitions)
+    : RequestHandler<UpsertEmailTemplateDefinitionCommand, ServiceResult<EmailTemplateDefinitionDto>>(logger)
+{
+    protected override async Task<ServiceResult<EmailTemplateDefinitionDto>> DoOnHandle(UpsertEmailTemplateDefinitionCommand request, CancellationToken cancellationToken)
+    {
+        try
+        {
+            var definition = await definitions.UpsertDefinitionAsync(request.Patch, cancellationToken);
+            return definition is null
+                ? Failure<EmailTemplateDefinitionDto>("Service not found.", ServiceErrorCode.NotFound)
+                : Success(TemplateDefinitionMapping.Map(definition));
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<EmailTemplateDefinitionDto>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminDeletionTests.cs

@@ -0,0 +1,137 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using System.Text.RegularExpressions;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using Microsoft.AspNetCore.TestHost;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminDeletionTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task DefinitionDeleteRequiresAntiforgeryAndConfirmation_AndPreservesFilter()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null, "en", "uk"));
+        var definition = await context.ReadAsync();
+        var url = $"/admin/services/{context.ServiceId}/templates/{definition.GetProperty("id").GetGuid()}/delete";
+        var html = await client.GetStringAsync(url + "?keyFilter=Welcome");
+        Assert.Contains("2 translation(s)", html);
+        Assert.Contains("Languages: en, uk", html);
+        var fields = TemplateEditorTestFields.Read(html);
+        Assert.Equal(HttpStatusCode.BadRequest, (await client.PostAsync(url, new FormUrlEncodedContent(new Dictionary<string, string> { ["ConfirmDelete"] = "true" }))).StatusCode);
+        var unconfirmed = await (await client.PostAsync(url, new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync();
+        Assert.Contains("Confirm deletion", unconfirmed);
+        AssertConfirmationReset(unconfirmed);
+        fields = TemplateEditorTestFields.Read(unconfirmed);
+        fields["ConfirmDelete"] = "true";
+        fields["Key"] = "Different";
+        var deleted = await client.PostAsync(url, new FormUrlEncodedContent(fields));
+        Assert.Equal(HttpStatusCode.Redirect, deleted.StatusCode);
+        Assert.Equal($"/admin/services/{context.ServiceId}?key=Welcome", deleted.Headers.Location!.OriginalString);
+        Assert.Equal(HttpStatusCode.NotFound, (await client.GetAsync(url)).StatusCode);
+        Assert.Equal(HttpStatusCode.OK, (await client.GetAsync($"/admin/services/{context.ServiceId}")).StatusCode);
+    }
+
+    [Fact]
+    public async Task StaleDefinitionConfirmationRefreshesCountRevisionAndUncheckedConfirmation()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null));
+        var definition = await context.ReadAsync();
+        var url = $"/admin/services/{context.ServiceId}/templates/{definition.GetProperty("id").GetGuid()}/delete";
+        var fields = TemplateEditorTestFields.Read(await context.Client.GetStringAsync(url));
+        var oldRevision = fields["Revision"];
+        await context.UpsertAsync(DefinitionApiTestContext.Body(definition.GetProperty("revision").GetGuid(), "en"));
+        fields["ConfirmDelete"] = "true";
+        var html = await (await context.Client.PostAsync(url, new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync();
+        Assert.Contains("revision changed", html);
+        Assert.Contains("1 translation(s)", html);
+        Assert.NotEqual(oldRevision, TemplateEditorTestFields.Read(html)["Revision"]);
+        AssertConfirmationReset(html);
+        Assert.Single((await context.ReadAsync()).GetProperty("translations").EnumerateArray());
+        var wrongScope = $"/admin/services/{Guid.NewGuid()}/templates/{definition.GetProperty("id").GetGuid()}/delete";
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync(wrongScope)).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.PostAsync(wrongScope, new FormUrlEncodedContent(fields))).StatusCode);
+    }
+
+    [Fact]
+    public async Task ServiceDeleteIsBlockedByEmptyDefinition_AndRequiresFreshConfirmationAfterRename()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null));
+        var url = $"/admin/services/{context.ServiceId}/delete";
+        var blocked = await client.GetStringAsync(url);
+        Assert.Contains("1 template definition(s)", blocked);
+        Assert.Contains("Email channels are retained", blocked);
+        var fields = TemplateEditorTestFields.Read(blocked);
+        fields["ConfirmDelete"] = "true";
+        Assert.Contains("Remove every template definition", await (await client.PostAsync(url, new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync());
+        var definition = await context.ReadAsync();
+        await client.DeleteAsync(context.DefinitionUrl() + "&revision=" + definition.GetProperty("revision").GetGuid());
+        fields = TemplateEditorTestFields.Read(await client.GetStringAsync(url));
+        var oldRevision = fields["Revision"];
+        using (var scope = context.App.Services.CreateScope())
+        {
+            var services = scope.ServiceProvider.GetRequiredService<INotificationServiceRepository>();
+            var service = (await services.GetAsync(context.ServiceId))!;
+            service.Name = "Renamed Before Delete";
+            await services.SaveAsync(service, false);
+        }
+        fields["ConfirmDelete"] = "true";
+        var stale = await (await client.PostAsync(url, new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync();
+        Assert.Contains("revision changed", stale);
+        Assert.Contains("Renamed Before Delete", stale);
+        Assert.NotEqual(oldRevision, TemplateEditorTestFields.Read(stale)["Revision"]);
+        AssertConfirmationReset(stale);
+        fields = TemplateEditorTestFields.Read(stale);
+        Assert.Contains("Confirm deletion", await (await client.PostAsync(url, new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync());
+        fields["ConfirmDelete"] = "true";
+        var deleted = await client.PostAsync(url, new FormUrlEncodedContent(fields));
+        Assert.Equal(HttpStatusCode.Redirect, deleted.StatusCode);
+        Assert.Equal("/admin/services", deleted.Headers.Location!.OriginalString);
+    }
+
+    [Fact]
+    public async Task EmptyStatesOfferScopedFirstCreateOrClearFilterActions()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var root = $"/admin/services/{context.ServiceId}";
+        var templates = await context.Client.GetStringAsync(root);
+        Assert.Contains("No email templates for this service yet.", templates);
+        Assert.Contains("Create First Template", templates);
+        Assert.Contains(root + "/templates/create", templates);
+        Assert.Contains("template-key-filter", templates);
+        var filtered = await context.Client.GetStringAsync(root + "?key=Missing");
+        Assert.Contains("No templates match this key.", filtered);
+        Assert.Contains(">Clear filter</a>", filtered);
+        Assert.DoesNotContain("Create First Template", filtered);
+        var service = (await context.Client.GetFromJsonAsync<JsonElement>(context.ServiceRoot)).GetProperty("data");
+        await context.Client.DeleteAsync(context.ServiceRoot + "?revision=" + service.GetProperty("revision").GetGuid());
+        var services = await context.Client.GetStringAsync("/admin/services");
+        Assert.Contains("No services yet.", services);
+        Assert.Contains("Create First Service", services);
+        Assert.Contains("aria-hidden=\"true\"", services);
+    }
+
+    [Fact]
+    public async Task TemplateLoadFailureDoesNotPretendTheServiceHasNoTemplates()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var failing = context.App.WithWebHostBuilder(builder => builder.ConfigureTestServices(services =>
+            services.AddScoped<IEmailTemplateDefinitionRepository, UnavailableEmailTemplateDefinitionRepository>()));
+        using var client = failing.CreateClient();
+        var html = await client.GetStringAsync($"/admin/services/{context.ServiceId}");
+        Assert.Contains("Could not load templates", html);
+        Assert.Contains("Templates are unavailable", html);
+        Assert.DoesNotContain("Create First Template", html);
+        Assert.DoesNotContain("No email templates for this service yet.", html);
+    }
+
+    private static void AssertConfirmationReset(string html) =>
+        Assert.DoesNotContain("checked", Regex.Match(html, "<input[^>]+type=\"checkbox\"[^>]*>").Value);
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminNavigationTests.cs

@@ -0,0 +1,60 @@
+using System.Net;
+using System.Text.RegularExpressions;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminNavigationTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task LayoutLinksToApiDocumentationInNewTab_AndScalarIsAvailable()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var pages = new[] { "/admin/services", "/admin/channels", "/admin/services/create", "/admin/channels/create" };
+        foreach (var page in pages)
+        {
+            var html = await context.Client.GetStringAsync(page);
+            Assert.Single(Regex.Matches(html, "class=\"admin-api-documentation\""));
+            Assert.Contains("href=\"/scalar/v1\" target=\"_blank\" rel=\"noopener noreferrer\"", html);
+            Assert.Contains("aria-label=\"API documentation (opens in a new tab)\">API documentation</a>", html);
+        }
+        Assert.Equal(HttpStatusCode.OK, (await context.Client.GetAsync("/scalar/v1")).StatusCode);
+    }
+
+    [Fact]
+    public async Task BothListTablesHaveScopedGridBorders_AndRetainTemplateHeaderOnFilterMiss()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var services = await context.Client.GetStringAsync("/admin/services");
+        Assert.Contains("table table-hover admin-data-table", services);
+        var templates = await context.Client.GetStringAsync($"/admin/services/{context.ServiceId}?key=Missing");
+        Assert.Contains("table table-hover admin-data-table service-template-grid", templates);
+        Assert.Contains("class=\"template-actions\"", templates);
+        Assert.Contains("No templates match this key.", templates);
+        Assert.Contains("class=\"template-key-filter\"", templates);
+    }
+    [Fact]
+    public async Task AllFourDataTablesShareTheGridClassAndScopedColumnHeaders()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var scope = context.App.Services.CreateScope();
+        await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().AddAsync(new EmailChannel
+        {
+            ServiceName = "TestService", EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings { Host = "localhost", FromEmail = "test@example.invalid" }
+        });
+        await scope.ServiceProvider.GetRequiredService<NotificationDbContext>().SaveChangesAsync();
+        var pages = new[] { "/admin/services", $"/admin/services/{context.ServiceId}", "/admin/channels", $"/admin/services/{context.ServiceId}/edit" };
+        foreach (var page in pages)
+        {
+            var html = await context.Client.GetStringAsync(page);
+            Assert.Single(Regex.Matches(html, "<table[^>]+admin-data-table"));
+            Assert.Equal(Regex.Matches(html, "<th[ >]").Count, Regex.Matches(html, "<th scope=\"col\"").Count);
+            Assert.DoesNotContain("<thead class=\"table-dark\">", html);
+        }
+    }
+
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminSmtpEditorViewTests.cs

@@ -0,0 +1,34 @@
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminSmtpEditorViewTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task ExistingChannelTestIncludesIdWithoutRenderingSavedPassword()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var scope = context.App.Services.CreateScope();
+        var channel = new EmailChannel
+        {
+            ServiceName = "TestService",
+            EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "smtp.example.invalid", Username = "test-user",
+                Password = "saved-secret-must-not-render", FromEmail = "sender@example.invalid"
+            }
+        };
+        await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().AddAsync(channel);
+        await scope.ServiceProvider.GetRequiredService<NotificationDbContext>().SaveChangesAsync();
+
+        var html = await context.Client.GetStringAsync($"/admin/channels/{channel.Id}");
+
+        Assert.Contains($"value=\"{channel.Id}\"", html);
+        Assert.Contains("const channelId = form.querySelector('[name=\"Id\"]').value", html);
+        Assert.DoesNotContain("saved-secret-must-not-render", html);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminSmtpSaveTests.cs

@@ -0,0 +1,136 @@
+using System.Net;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminSmtpSaveTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task BlankPasswordKeepsSavedValueWhenOnlySenderChanges()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["UseSsl"] = "true";
+        fields["Password"] = "";
+        fields["FromName"] = "Updated sender";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+
+        Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
+        var saved = await ReadSettings(context, channel.Id);
+        Assert.Equal("saved-test-secret", saved.Password);
+        Assert.Equal("Updated sender", saved.FromName);
+    }
+
+    [Theory]
+    [InlineData("Host", "other.example.invalid")]
+    [InlineData("Port", "2525")]
+    [InlineData("Username", "other-user")]
+    [InlineData("UseSsl", "false")]
+    public async Task ChangedConnectionWithBlankPasswordIsRejected(string field, string value)
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["UseSsl"] = "true";
+        fields["Password"] = "";
+        fields[field] = value;
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+        var html = await response.Content.ReadAsStringAsync();
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Contains("Enter the password to save changed SMTP connection settings.", html);
+        Assert.DoesNotContain("saved-test-secret", html);
+        var saved = await ReadSettings(context, channel.Id);
+        Assert.Equal("saved-test-secret", saved.Password);
+        Assert.Equal("smtp.example.invalid", saved.Host);
+    }
+
+    [Fact]
+    public async Task ExplicitPasswordCanReplaceSavedValue()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["UseSsl"] = "true";
+        fields["Password"] = "replacement-test-secret";
+        fields["Host"] = "other.example.invalid";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+
+        Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
+        var saved = await ReadSettings(context, channel.Id);
+        Assert.Equal("replacement-test-secret", saved.Password);
+        Assert.Equal("other.example.invalid", saved.Host);
+    }
+
+    [Fact]
+    public async Task NewChannelStillRequiresPassword()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync("/admin/channels/create"));
+        fields["ServiceName"] = "NewTestService";
+        fields["Host"] = "smtp.example.invalid";
+        fields["Username"] = "test-user";
+        fields["FromEmail"] = "sender@example.invalid";
+        fields["FromName"] = "Sender";
+        fields["Password"] = "";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Contains("The Password field is required.", await response.Content.ReadAsStringAsync());
+    }
+
+    [Fact]
+    public async Task InvalidFormDoesNotRenderEnteredPassword()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var channel = await SeedChannel(context);
+        using var client = context.App.CreateClient(new() { AllowAutoRedirect = false });
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync($"/admin/channels/{channel.Id}"));
+        fields["Password"] = "replacement-test-secret";
+        fields["FromEmail"] = "invalid-address";
+
+        var response = await client.PostAsync("/admin/channels/save", new FormUrlEncodedContent(fields));
+        var html = await response.Content.ReadAsStringAsync();
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.DoesNotContain("replacement-test-secret", html);
+        Assert.Equal("saved-test-secret", (await ReadSettings(context, channel.Id)).Password);
+    }
+
+    private static async Task<EmailChannel> SeedChannel(DefinitionApiTestContext context)
+    {
+        using var scope = context.App.Services.CreateScope();
+        var channel = new EmailChannel
+        {
+            ServiceName = "TestService", EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "smtp.example.invalid", Port = 587, Username = "test-user",
+                Password = "saved-test-secret", UseSsl = true,
+                FromEmail = "sender@example.invalid", FromName = "Original sender"
+            }
+        };
+        await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().AddAsync(channel);
+        await scope.ServiceProvider.GetRequiredService<NotificationDbContext>().SaveChangesAsync();
+        return channel;
+    }
+
+    private static async Task<SmtpChannelSettings> ReadSettings(DefinitionApiTestContext context, Guid id)
+    {
+        using var scope = context.App.Services.CreateScope();
+        var channel = await scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>().GetByIdAsync(id);
+        return Assert.IsType<SmtpChannelSettings>(channel?.Settings);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminSmtpTestControllerTests.cs

@@ -0,0 +1,112 @@
+using System.Reflection;
+using System.Text.Json;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.Web.Controllers.Admin;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminSmtpTestControllerTests
+{
+    private static readonly Guid ChannelId = Guid.NewGuid();
+
+    [Fact]
+    public async Task BlankPasswordUsesSavedSecretAndCurrentUnsavedSender()
+    {
+        var (controller, recorder) = CreateController();
+        var response = await controller.TestSmtp(Request(), CancellationToken.None);
+
+        Assert.True(Succeeded(response));
+        Assert.Equal("saved-test-secret", recorder.SentCommand?.Password);
+        Assert.Equal("changed@example.invalid", recorder.SentCommand?.FromEmail);
+        Assert.Equal("Changed sender", recorder.SentCommand?.FromName);
+        Assert.Equal(1, recorder.LookupCount);
+        Assert.DoesNotContain("saved-test-secret", JsonSerializer.Serialize(((OkObjectResult)response).Value));
+    }
+
+    [Fact]
+    public async Task ExplicitPasswordOverridesSavedWithoutLookup()
+    {
+        var (controller, recorder) = CreateController();
+        var response = await controller.TestSmtp(Request() with { Password = "typed-test-secret" }, CancellationToken.None);
+
+        Assert.True(Succeeded(response));
+        Assert.Equal("typed-test-secret", recorder.SentCommand?.Password);
+        Assert.Equal(0, recorder.LookupCount);
+    }
+
+    [Theory]
+    [InlineData("host")]
+    [InlineData("port")]
+    [InlineData("username")]
+    [InlineData("ssl")]
+    public async Task ChangedConnectionRequiresExplicitPassword(string field)
+    {
+        var (controller, recorder) = CreateController();
+        var request = field switch
+        {
+            "host" => Request() with { Host = "other.example.invalid" },
+            "port" => Request() with { Port = 2525 },
+            "username" => Request() with { Username = "other-user" },
+            _ => Request() with { UseSsl = false }
+        };
+
+        var response = await controller.TestSmtp(request, CancellationToken.None);
+
+        Assert.False(Succeeded(response));
+        Assert.Null(recorder.SentCommand);
+    }
+
+    [Fact]
+    public async Task UnknownChannelDoesNotSend()
+    {
+        var (controller, recorder) = CreateController();
+        recorder.Channel = null;
+
+        var response = await controller.TestSmtp(Request(), CancellationToken.None);
+
+        Assert.False(Succeeded(response));
+        Assert.Null(recorder.SentCommand);
+    }
+
+    [Fact]
+    public async Task NewChannelKeepsAdHocTestBehavior()
+    {
+        var (controller, recorder) = CreateController();
+
+        var response = await controller.TestSmtp(Request() with { ChannelId = null }, CancellationToken.None);
+
+        Assert.True(Succeeded(response));
+        Assert.Equal(string.Empty, recorder.SentCommand?.Password);
+        Assert.Equal(0, recorder.LookupCount);
+    }
+
+    private static (AdminChannelsController Controller, RecordingAdminSmtpMediator Recorder) CreateController()
+    {
+        var mediator = DispatchProxy.Create<IMediator, RecordingAdminSmtpMediator>();
+        var recorder = (RecordingAdminSmtpMediator)mediator;
+        recorder.Channel = new EmailChannel
+        {
+            Id = ChannelId,
+            ServiceName = "TestService",
+            EmailChannelType = EmailChannelType.Smtp,
+            Settings = new SmtpChannelSettings
+            {
+                Host = "smtp.example.invalid", Port = 587,
+                Username = "test-user", Password = "saved-test-secret", UseSsl = true
+            }
+        };
+        return (new AdminChannelsController(mediator), recorder);
+    }
+
+    private static TestSmtpRequest Request() => new(
+        "smtp.example.invalid", 587, "test-user", "", true,
+        "changed@example.invalid", "Changed sender", "recipient@example.invalid", ChannelId);
+
+    private static bool Succeeded(IActionResult response)
+    {
+        var body = JsonSerializer.Serialize(((OkObjectResult)response).Value);
+        return JsonDocument.Parse(body).RootElement.GetProperty("success").GetBoolean();
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/AdminTemplatesIndexViewTests.cs

@@ -0,0 +1,14 @@
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class AdminTemplatesIndexViewTests
+{
+    [Fact]
+    public void CreateAndEditLinks_KeepTheirServiceAndKeyFilter()
+    {
+        string view = File.ReadAllText(Path.Combine(AppContext.BaseDirectory, "TestViews", "Index.cshtml"));
+        Assert.Contains("asp-route-serviceId=\"@serviceId\"", view);
+        Assert.Contains("asp-route-keyFilter=\"@keyFilter\"", view);
+        Assert.Contains("new { serviceId, definitionId = template.Id, keyFilter }", view);
+        Assert.DoesNotContain("/admin/templates", view);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/DefinitionApiTestContext.cs

@@ -0,0 +1,47 @@
+using System.Net.Http.Json;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class DefinitionApiTestContext : IAsyncDisposable
+{
+    public required TemplateWebApplicationFactory App { get; init; }
+    public required HttpClient Client { get; init; }
+    public required Guid ServiceId { get; init; }
+    public string ServiceRoot => $"/api/v1/services/{ServiceId}";
+
+    public static async Task<DefinitionApiTestContext> CreateAsync(TemplateDatabaseFixture fixture)
+    {
+        var app = new TemplateWebApplicationFactory(await fixture.CreateDatabaseAsync());
+        var client = app.CreateClient();
+        var response = await client.GetFromJsonAsync<JsonElement>("/api/v1/services?name=TestService");
+        return new DefinitionApiTestContext { App = app, Client = client, ServiceId = response.GetProperty("data").GetProperty("id").GetGuid() };
+    }
+
+    public string DefinitionUrl(string key = "Welcome", bool upsert = false) =>
+        ServiceRoot + "/email-template-definitions" + (upsert ? "/upsert" : "") + "?key=" + Uri.EscapeDataString(key);
+
+    public Task<HttpResponseMessage> UpsertAsync(JsonNode body, string key = "Welcome") =>
+        Client.PostAsJsonAsync(DefinitionUrl(key, upsert: true), body);
+
+    public async Task<JsonElement> ReadAsync(string key = "Welcome") =>
+        (await Client.GetFromJsonAsync<JsonElement>(DefinitionUrl(key))).GetProperty("data");
+
+    public static JsonObject Body(Guid? revision, params string[] codes) => new()
+    {
+        ["revision"] = revision?.ToString(),
+        ["variables"] = new JsonArray(new JsonObject { ["name"] = "Name", ["required"] = true }),
+        ["translations"] = new JsonArray(codes.Select(code => (JsonNode)new JsonObject
+        {
+            ["languageCode"] = code, ["subject"] = "Subject " + code,
+            ["htmlBody"] = "<p>Hello {{Name}}</p>", ["textBody"] = "Hello {{Name}}"
+        }).ToArray())
+    };
+
+    public async ValueTask DisposeAsync()
+    {
+        Client.Dispose();
+        await App.DisposeAsync();
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/EditorLayoutTests.cs

@@ -0,0 +1,68 @@
+using System.Text.RegularExpressions;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class EditorLayoutTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task ServiceAndTemplateEditorsRenderOneBreadcrumbBeforeTheCard_IncludingValidationErrors()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient();
+        using var scope = app.Services.CreateScope();
+        var service = (await scope.ServiceProvider.GetRequiredService<INotificationServiceRepository>().GetAllAsync()).Single();
+        var definition = new EmailTemplateDefinition { ServiceName = service.Name, Key = "Layout" };
+        await scope.ServiceProvider.GetRequiredService<IEmailTemplateDefinitionRepository>().SaveDefinitionAsync(definition, true);
+        var root = $"/admin/services/{service.Id}";
+        var editors = new[]
+        {
+            (Url: "/admin/services/create", Title: "Create Service", Form: "serviceForm"),
+            (Url: root + "/edit", Title: "Edit Service", Form: "serviceForm"),
+            (Url: root + "/templates/create", Title: "Create Email Template", Form: "templateForm"),
+            (Url: root + "/templates/" + definition.Id, Title: "Edit Email Template", Form: "templateForm")
+        };
+        foreach (var editor in editors)
+            AssertEditorLayout(await client.GetStringAsync(editor.Url), editor.Title, editor.Form);
+        var fields = TemplateEditorTestFields.Read(await client.GetStringAsync(root + "/templates/create"));
+        fields["Key"] = "InvalidDraft";
+        fields["VariablesJson"] = "{invalid";
+        var errorHtml = await (await client.PostAsync(root + "/templates/save", new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync();
+        Assert.Contains("Invalid variables JSON", errorHtml);
+        AssertEditorLayout(errorHtml, "Create Email Template", "templateForm");
+        Assert.Contains("<dl class=\"template-service-context\">", errorHtml);
+        Assert.Contains("<dt>Service</dt>", errorHtml);
+        Assert.Contains("<dd>TestService</dd>", errorHtml);
+        Assert.DoesNotContain("form-control-plaintext", errorHtml);
+        Assert.Equal(service.Name, TemplateEditorTestFields.Read(errorHtml)["ServiceName"]);
+    }
+
+    [Fact]
+    public async Task ChannelEditorWorksWithoutTheOptionalBreadcrumbSection()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient();
+        var html = await client.GetStringAsync("/admin/channels/create");
+        Assert.Contains("<h1 class=\"editor-card-title\">", html);
+        Assert.Contains("<span>Create Channel</span>", html);
+        Assert.Contains("id=\"channelForm\"", html);
+        Assert.DoesNotContain("aria-label=\"Breadcrumb\"", html);
+    }
+
+    private static void AssertEditorLayout(string html, string title, string form)
+    {
+        Assert.Single(Regex.Matches(html, "aria-label=\"Breadcrumb\""));
+        var breadcrumb = html.IndexOf("<nav aria-label=\"Breadcrumb\"", StringComparison.Ordinal);
+        var card = html.IndexOf("<div class=\"card editor-card\">", StringComparison.Ordinal);
+        Assert.True(breadcrumb >= 0 && breadcrumb < card);
+        Assert.Single(Regex.Matches(html, "<h1 class=\"editor-card-title\">"));
+        Assert.Contains("aria-hidden=\"true\"", html);
+        Assert.Contains("<span>" + title + "</span>", html);
+        Assert.Contains("id=\"" + form + "\"", html);
+        Assert.Contains("aria-current=\"page\"", html);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/EmailChannelApiTests.cs

@@ -0,0 +1,92 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using HrynCo.NotificationService.DAL.Abstract.Providers;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class EmailChannelApiTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task SmtpSettingsRoundTripThroughCreateReadUpdateListAndDelete()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var request = Content("smtp.example.invalid", 2525, "test-only-user");
+        var created = await context.Client.PostAsJsonAsync("/api/v1/email-channels", request);
+        Assert.Equal(HttpStatusCode.Created, created.StatusCode);
+        var id = (await created.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("data").GetGuid();
+        var original = (await context.Client.GetFromJsonAsync<JsonElement>($"/api/v1/email-channels/{id}")).GetProperty("data");
+        Assert.Equal("smtp.example.invalid", original.GetProperty("settings").GetProperty("host").GetString());
+        Assert.Equal(2525, original.GetProperty("settings").GetProperty("port").GetInt32());
+        Assert.Equal("test-only-user", original.GetProperty("settings").GetProperty("username").GetString());
+        Assert.Equal(HttpStatusCode.OK, (await context.Client.PutAsJsonAsync($"/api/v1/email-channels/{id}", Content("updated.example.invalid", 2526, "updated-user"))).StatusCode);
+        var all = (await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/email-channels/all")).GetProperty("data");
+        var updated = Assert.Single(all.EnumerateArray());
+        Assert.Equal("updated.example.invalid", updated.GetProperty("settings").GetProperty("host").GetString());
+        Assert.Equal("updated-user", updated.GetProperty("settings").GetProperty("username").GetString());
+        Assert.Equal(2526, updated.GetProperty("settings").GetProperty("port").GetInt32());
+        Assert.Equal("test-only-value", updated.GetProperty("settings").GetProperty("password").GetString());
+        Assert.False(updated.GetProperty("settings").GetProperty("useSsl").GetBoolean());
+        Assert.Equal("sender@example.invalid", updated.GetProperty("settings").GetProperty("fromEmail").GetString());
+        Assert.Equal("Test sender", updated.GetProperty("settings").GetProperty("fromName").GetString());
+        var filtered = await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/email-channels?serviceName=IndependentChannelService");
+        Assert.Single(filtered.GetProperty("data").EnumerateArray());
+        Assert.Equal(HttpStatusCode.OK, (await context.Client.DeleteAsync($"/api/v1/email-channels/{id}")).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync($"/api/v1/email-channels/{id}")).StatusCode);
+        Assert.Empty((await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/email-channels/all")).GetProperty("data").EnumerateArray());
+    }
+
+    [Fact]
+    public async Task GetAllIncludesChannelsWhoseServiceNameHasNoServiceRecord()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var scope = context.App.Services.CreateScope();
+        var channels = scope.ServiceProvider.GetRequiredService<IEmailChannelRepository>();
+        foreach (var serviceName in new[] { "TestService", "OrphanChannelService" })
+            await channels.AddAsync(new EmailChannel
+            {
+                ServiceName = serviceName, EmailChannelType = EmailChannelType.Smtp,
+                Settings = new SmtpChannelSettings { Host = "localhost", FromEmail = "test@example.invalid" }
+            });
+        await scope.ServiceProvider.GetRequiredService<NotificationDbContext>().SaveChangesAsync();
+        var all = (await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/email-channels/all")).GetProperty("data");
+        Assert.Equal(2, all.GetArrayLength());
+        Assert.Contains(all.EnumerateArray(), c => c.GetProperty("serviceName").GetString() == "OrphanChannelService");
+        Assert.All(all.EnumerateArray(), c => Assert.NotEqual(Guid.Empty, c.GetProperty("id").GetGuid()));
+    }
+
+    [Theory]
+    [InlineData("nullSettings")]
+    [InlineData("invalidPort")]
+    [InlineData("blankHost")]
+    [InlineData("unsupportedType")]
+    [InlineData("blankService")]
+    public async Task InvalidSmtpCreateReturnsValidationEnvelopeWithoutPersisting(string scenario)
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var body = JsonSerializer.SerializeToNode(Content("smtp.example.invalid", 2525, "test-user"), new JsonSerializerOptions(JsonSerializerDefaults.Web))!.AsObject();
+        switch (scenario)
+        {
+            case "nullSettings": body["settings"] = null; break;
+            case "invalidPort": body["settings"]!["port"] = 0; break;
+            case "blankHost": body["settings"]!["host"] = " "; break;
+            case "unsupportedType": body["channelType"] = 99; break;
+            case "blankService": body["serviceName"] = " "; break;
+        }
+        var response = await context.Client.PostAsJsonAsync("/api/v1/email-channels", body);
+        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+        Assert.Equal("InvalidRequest", (await response.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("error").GetProperty("code").GetString());
+        Assert.Empty((await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/email-channels/all")).GetProperty("data").EnumerateArray());
+    }
+
+    private static object Content(string host, int port, string username) => new
+    {
+        serviceName = "IndependentChannelService", priority = 1, channelType = 1,
+        settings = new { host, port, username, password = "test-only-value", useSsl = false, fromEmail = "sender@example.invalid", fromName = "Test sender" },
+        dailyLimit = 100, monthlyLimit = 1000, warnThresholdPercent = 90, isActive = true
+    };
+}

HrynCo.NotificationService.Web.IntegrationTests/EmailTemplateApiTests.cs

@@ -0,0 +1,212 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using System.Text.RegularExpressions;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.AspNetCore.TestHost;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class EmailTemplateApiTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task LegacyApi_CreatesReadsUpdatesAndDeletesLanguageVersions_WithoutContractDivergence()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient();
+        var created = await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        Assert.Equal(HttpStatusCode.Created, created.StatusCode);
+        var originalId = (await created.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("data").GetGuid();
+        Assert.Equal(HttpStatusCode.Created, (await client.PostAsJsonAsync("/api/v1/email-templates", Content("uk"))).StatusCode);
+        Assert.Equal(HttpStatusCode.Conflict, (await client.PostAsJsonAsync("/api/v1/email-templates", Content("de", "Other"))).StatusCode);
+        Assert.Equal(HttpStatusCode.Conflict, (await client.PutAsJsonAsync("/api/v1/email-templates/TestService/Welcome/en", Content("en", "Other"))).StatusCode);
+        Assert.Equal(HttpStatusCode.OK, (await client.PutAsJsonAsync("/api/v1/email-templates/TestService/Welcome/uk", Content("uk", subject: "Updated uk"))).StatusCode);
+        var all = await client.GetFromJsonAsync<JsonElement>("/api/v1/email-templates?serviceName=TestService&key=Welcome");
+        Assert.Equal(2, all.GetProperty("data").GetArrayLength());
+        var en = await ReadAsync(client, "en");
+        Assert.Equal(originalId, en.GetProperty("id").GetGuid());
+        Assert.Equal("Subject en", en.GetProperty("subject").GetString());
+        Assert.Equal(HttpStatusCode.OK, (await client.DeleteAsync("/api/v1/email-templates/TestService/Welcome/uk")).StatusCode);
+        Assert.Equal(HttpStatusCode.OK, (await client.DeleteAsync("/api/v1/email-templates/TestService/Welcome/en")).StatusCode);
+        Assert.Contains("data-state=\"missing\"", await client.GetStringAsync("/admin/templates?serviceName=TestService"));
+        Assert.Equal(HttpStatusCode.NotFound, (await client.GetAsync("/api/v1/email-templates/TestService/Welcome/de")).StatusCode);
+    }
+
+    [Fact]
+    public async Task ConcurrentLegacyCreates_OnlyPersistOneLanguage()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient();
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        var responses = await Task.WhenAll(
+            client.PostAsJsonAsync("/api/v1/email-templates", Content("uk")),
+            client.PostAsJsonAsync("/api/v1/email-templates", Content("uk")));
+        Assert.Equal(1, responses.Count(r => r.StatusCode == HttpStatusCode.Created));
+        Assert.Equal(1, responses.Count(r => r.StatusCode == HttpStatusCode.Conflict));
+    }
+
+    [Fact]
+    public async Task GroupEditor_SharedContractIsSavedForAllLanguages_AndPreservesContentIdsAndFilters()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient(new() { AllowAutoRedirect = false });
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("uk"));
+        var originalId = (await ReadAsync(client, "uk")).GetProperty("id").GetGuid();
+        var fields = await EditorFieldsAsync(client);
+        fields["VariablesJson"] = """[{"name":"Shared","required":true}]""";
+        fields["KeyFilter"] = "Welcome";
+        fields["Languages[0].Subject"] = "Edited English";
+        var response = await client.PostAsync(SaveUrl(fields), new FormUrlEncodedContent(fields));
+        Assert.Equal(HttpStatusCode.Redirect, response.StatusCode);
+        Assert.Equal($"/admin/services/{fields["ServiceId"]}?key=Welcome", response.Headers.Location!.OriginalString);
+        var uk = await ReadAsync(client, "uk");
+        Assert.Equal(originalId, uk.GetProperty("id").GetGuid());
+        Assert.Equal("Subject uk", uk.GetProperty("subject").GetString());
+        Assert.Equal("Shared", uk.GetProperty("variables")[0].GetProperty("name").GetString());
+        Assert.Equal("Edited English", (await ReadAsync(client, "en")).GetProperty("subject").GetString());
+        var html = await client.GetStringAsync($"/admin/services/{fields["ServiceId"]}?key=Welcome");
+        Assert.Single(Regex.Matches(html, "<td>Welcome</td>"));
+        Assert.Contains("data-language-code=\"en\" data-state=\"present\"", html);
+        Assert.Contains("data-language-code=\"uk\" data-state=\"present\"", html);
+        Assert.Contains("keyFilter=Welcome", html);
+        Assert.DoesNotContain("@filterQuery", html);
+    }
+
+    [Theory]
+    [InlineData("{broken", "Invalid variables JSON")]
+    [InlineData("null", "Variables must be a JSON array")]
+    [InlineData("[{\"name\":\"Name\",\"required\":true},{\"name\":\"Name\",\"required\":false}]", "Variable names must be unique")]
+    public async Task InvalidSharedContract_KeepsEnteredValuesAndPersistsNothing(string json, string error)
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient();
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("uk"));
+        var fields = await EditorFieldsAsync(client);
+        fields["VariablesJson"] = json;
+        fields["Languages[1].Subject"] = "Unsaved Ukrainian";
+        fields["ActiveLanguageIndex"] = "1";
+        var response = await client.PostAsync(SaveUrl(fields), new FormUrlEncodedContent(fields));
+        var html = await response.Content.ReadAsStringAsync();
+        Assert.Contains(error, html);
+        Assert.Contains("Unsaved Ukrainian", html);
+        Assert.Contains("name=\"ActiveLanguageIndex\" value=\"1\"", html);
+        Assert.Equal("Subject uk", (await ReadAsync(client, "uk")).GetProperty("subject").GetString());
+    }
+
+    [Fact]
+    public async Task DuplicateLanguageIncompleteContentAndStaleSave_AreRejectedAtomically()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient();
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("uk"));
+        var fields = await EditorFieldsAsync(client);
+        fields["Languages[1].LanguageCode"] = "en";
+        Assert.Contains("Language codes must be unique", await PostEditorAsync(client, fields));
+        fields["Languages[1].LanguageCode"] = "uk";
+        fields["Languages[1].TextBody"] = "";
+        Assert.Contains("TextBody field is required", await PostEditorAsync(client, fields));
+        fields["Languages[1].TextBody"] = "Restored text";
+        await client.PutAsJsonAsync("/api/v1/email-templates/TestService/Welcome/en", Content("en", subject: "Concurrent change"));
+        Assert.Contains("changed after you opened it", await PostEditorAsync(client, fields));
+        Assert.Equal("Concurrent change", (await ReadAsync(client, "en")).GetProperty("subject").GetString());
+        Assert.Equal("Subject uk", (await ReadAsync(client, "uk")).GetProperty("subject").GetString());
+    }
+
+    [Fact]
+    public async Task GroupEditor_RemovesOneLanguageAndAddsAnother_WithoutChangingRemainingLanguage()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var client = app.CreateClient(new() { AllowAutoRedirect = false });
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("uk"));
+        var fields = await EditorFieldsAsync(client);
+        fields["Languages[1].Subject"] = "";
+        fields["Languages[1].HtmlBody"] = "";
+        fields["Languages[1].TextBody"] = "";
+        AddLanguageFields(fields, 2, "de");
+        fields["Languages[2].Subject"] = "German";
+        Assert.Equal(HttpStatusCode.Redirect, (await client.PostAsync(SaveUrl(fields), new FormUrlEncodedContent(fields))).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await client.GetAsync("/api/v1/email-templates/TestService/Welcome/uk")).StatusCode);
+        Assert.Equal("Subject en", (await ReadAsync(client, "en")).GetProperty("subject").GetString());
+        Assert.Equal("German", (await ReadAsync(client, "de")).GetProperty("subject").GetString());
+    }
+
+    [Fact]
+    public async Task FailedSave_ShowsActionableErrorAndKeepsEnteredValues()
+    {
+        var connection = await fixture.CreateDatabaseAsync();
+        await using var app = new TemplateWebApplicationFactory(connection);
+        using var failingApp = app.WithWebHostBuilder(builder => builder.ConfigureTestServices(services =>
+            services.AddScoped<IEmailTemplateDefinitionRepository, FailingEmailTemplateDefinitionRepository>()));
+        using var client = failingApp.CreateClient();
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("en"));
+        await client.PostAsJsonAsync("/api/v1/email-templates", Content("uk"));
+        var fields = await EditorFieldsAsync(client);
+        fields["Languages[1].Subject"] = "Unsaved after failure";
+        var html = await PostEditorAsync(client, fields);
+        Assert.Contains("Could not save the template", html);
+        Assert.Contains("Unsaved after failure", html);
+        Assert.Equal("Subject uk", (await ReadAsync(client, "uk")).GetProperty("subject").GetString());
+    }
+
+    private static object Content(string language, string variable = "Name", string? subject = null) => new
+    {
+        serviceName = "TestService", key = "Welcome", languageCode = language,
+        subject = subject ?? "Subject " + language, htmlBody = "<p>Hello {{Name}}</p>", textBody = "Hello {{Name}}",
+        variables = new[] { new { name = variable, required = true } }
+    };
+
+    private static async Task<JsonElement> ReadAsync(HttpClient client, string language) =>
+        (await client.GetFromJsonAsync<JsonElement>("/api/v1/email-templates/TestService/Welcome/" + language)).GetProperty("data");
+
+    private static async Task<Dictionary<string, string>> EditorFieldsAsync(HttpClient client)
+    {
+        var response = await client.GetAsync("/admin/templates/TestService/Welcome/uk");
+        var html = response.Headers.Location is Uri location ? await client.GetStringAsync(location) : await response.Content.ReadAsStringAsync();
+        var fields = new Dictionary<string, string>();
+        foreach (Match input in Regex.Matches(html, "<input[^>]+>"))
+        {
+            var name = Regex.Match(input.Value, "name=\"([^\"]+)\"");
+            var value = Regex.Match(input.Value, "value=\"([^\"]*)\"");
+            if (name.Success && value.Success)
+                fields[WebUtility.HtmlDecode(name.Groups[1].Value)] = WebUtility.HtmlDecode(value.Groups[1].Value);
+        }
+        foreach (var codeField in fields.Keys.Where(k => k.EndsWith(".LanguageCode")).ToList())
+        {
+            var prefix = codeField[..^"LanguageCode".Length];
+            fields.TryAdd(prefix + "Subject", "");
+            fields.TryAdd(prefix + "HtmlBody", "");
+            fields.TryAdd(prefix + "TextBody", "");
+        }
+        fields["ServiceName"] = "TestService";
+        fields["Key"] = "Welcome";
+        fields["VariablesJson"] = """[{"name":"Name","required":true}]""";
+        AddLanguageFields(fields, 0, "en");
+        AddLanguageFields(fields, 1, "uk");
+        return fields;
+    }
+
+    private static void AddLanguageFields(Dictionary<string, string> fields, int index, string language)
+    {
+        fields[$"Languages[{index}].LanguageCode"] = language;
+        fields[$"Languages[{index}].Subject"] = "Subject " + language;
+        fields[$"Languages[{index}].HtmlBody"] = "<p>Hello {{Name}}</p>";
+        fields[$"Languages[{index}].TextBody"] = "Hello {{Name}}";
+    }
+
+    private static string SaveUrl(Dictionary<string, string> fields) => $"/admin/services/{fields["ServiceId"]}/templates/save";
+
+    private static async Task<string> PostEditorAsync(HttpClient client, Dictionary<string, string> fields) =>
+        await (await client.PostAsync(SaveUrl(fields), new FormUrlEncodedContent(fields))).Content.ReadAsStringAsync();
+}

HrynCo.NotificationService.Web.IntegrationTests/EmailTemplateDefinitionApiTests.cs

@@ -0,0 +1,228 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class EmailTemplateDefinitionApiTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task ServiceReadsExposeExactCatalogAndStableIdentityThroughRename()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var service = (await context.Client.GetFromJsonAsync<JsonElement>(context.ServiceRoot)).GetProperty("data");
+        Assert.Equal(context.ServiceId, service.GetProperty("id").GetGuid());
+        Assert.Equal("TestService", service.GetProperty("name").GetString());
+        Assert.Equal(new[] { "de", "en", "ru", "ru-RU", "uk" }, service.GetProperty("supportedLanguageCodes").EnumerateArray().Select(c => c.GetString()));
+        Assert.Equal(5, service.EnumerateObject().Count());
+        Assert.NotEqual(Guid.Empty, service.GetProperty("revision").GetGuid());
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync("/api/v1/services?name=testservice")).StatusCode);
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.Client.GetAsync("/api/v1/services")).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync($"/api/v1/services/{Guid.NewGuid()}")).StatusCode);
+        using var scope = context.App.Services.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<INotificationServiceRepository>();
+        var model = (await repository.GetAsync(context.ServiceId))!;
+        model.Name = "Renamed Service";
+        await repository.SaveAsync(model, false);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync("/api/v1/services?name=TestService")).StatusCode);
+        var renamed = await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/services?name=Renamed%20Service");
+        Assert.Equal(context.ServiceId, renamed.GetProperty("data").GetProperty("id").GetGuid());
+        Assert.Equal("Renamed Service", (await context.Client.GetFromJsonAsync<JsonElement>(context.ServiceRoot)).GetProperty("data").GetProperty("name").GetString());
+    }
+
+    [Fact]
+    public async Task AtomicUpsertReplacesContractAndSentContent_AndRetainsOmittedTranslations()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        Assert.Equal(HttpStatusCode.Created, (await context.UpsertAsync(DefinitionApiTestContext.Body(null, "en", "uk"))).StatusCode);
+        var original = await context.ReadAsync();
+        var uk = original.GetProperty("translations")[1];
+        Assert.True(uk.GetProperty("created").GetDateTimeOffset().Year >= 2020);
+        var revision = original.GetProperty("revision").GetGuid();
+        var update = DefinitionApiTestContext.Body(revision, "en", "de");
+        update["variables"] = new JsonArray(new JsonObject { ["name"] = "Changed", ["required"] = false });
+        update["translations"]![0]!["subject"] = "Edited English";
+        var response = await context.UpsertAsync(update);
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var returned = (await response.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("data");
+        var saved = await context.ReadAsync();
+        Assert.Equal(saved.GetProperty("revision").GetGuid(), returned.GetProperty("revision").GetGuid());
+        Assert.NotEqual(revision, saved.GetProperty("revision").GetGuid());
+        Assert.Equal(original.GetProperty("id").GetGuid(), saved.GetProperty("id").GetGuid());
+        Assert.Equal(3, saved.GetProperty("translations").GetArrayLength());
+        Assert.Equal(uk.GetRawText(), saved.GetProperty("translations")[2].GetRawText());
+        Assert.Equal("Edited English", saved.GetProperty("translations")[1].GetProperty("subject").GetString());
+        Assert.Equal(original.GetProperty("translations")[0].GetProperty("id").GetGuid(), saved.GetProperty("translations")[1].GetProperty("id").GetGuid());
+        var legacy = await context.Client.GetFromJsonAsync<JsonElement>("/api/v1/email-templates/TestService/Welcome/uk");
+        Assert.Equal("Changed", legacy.GetProperty("data").GetProperty("variables")[0].GetProperty("name").GetString());
+        Assert.False(saved.GetProperty("variables")[0].GetProperty("required").GetBoolean());
+    }
+
+    [Fact]
+    public async Task ExplicitRemovalCanRemoveLastVersion_AndKeepDefinitionAndContract()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null, "en", "uk"));
+        var before = await context.ReadAsync();
+        var request = DefinitionApiTestContext.Body(before.GetProperty("revision").GetGuid());
+        request["removeLanguageCodes"] = new JsonArray("en", "uk", "de");
+        var response = await context.UpsertAsync(request);
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        var returned = (await response.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("data");
+        Assert.Empty(returned.GetProperty("translations").EnumerateArray());
+        var saved = await context.ReadAsync();
+        Assert.Equal(before.GetProperty("id").GetGuid(), saved.GetProperty("id").GetGuid());
+        Assert.Empty(saved.GetProperty("translations").EnumerateArray());
+        Assert.Single(saved.GetProperty("variables").EnumerateArray());
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync("/api/v1/email-templates/TestService/Welcome/en")).StatusCode);
+    }
+
+    [Fact]
+    public async Task RevisionsEnforceCreateOnlyAndUpdateOnly_WithoutPartialChanges()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null));
+        var before = await context.ReadAsync();
+        Assert.Equal(HttpStatusCode.Conflict, (await context.UpsertAsync(DefinitionApiTestContext.Body(null, "en"))).StatusCode);
+        Assert.Equal(HttpStatusCode.Conflict, (await context.UpsertAsync(DefinitionApiTestContext.Body(Guid.NewGuid(), "en"))).StatusCode);
+        Assert.Equal(HttpStatusCode.Conflict, (await context.UpsertAsync(DefinitionApiTestContext.Body(Guid.NewGuid(), "en"), "Missing")).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync(context.DefinitionUrl("Missing"))).StatusCode);
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.UpsertAsync(DefinitionApiTestContext.Body(Guid.Empty))).StatusCode);
+        Assert.Equal(before.GetRawText(), (await context.ReadAsync()).GetRawText());
+        var revision = before.GetProperty("revision").GetGuid();
+        Assert.Equal(HttpStatusCode.OK, (await context.UpsertAsync(DefinitionApiTestContext.Body(revision))).StatusCode);
+        Assert.Equal(HttpStatusCode.Conflict, (await context.UpsertAsync(DefinitionApiTestContext.Body(revision, "uk"))).StatusCode);
+        var otherRoot = $"/api/v1/services/{Guid.NewGuid()}/email-template-definitions/upsert?key=Welcome";
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.PostAsJsonAsync(otherRoot, DefinitionApiTestContext.Body(null))).StatusCode);
+    }
+
+    [Theory]
+    [InlineData("missingVariables")]
+    [InlineData("nullVariables")]
+    [InlineData("missingTranslations")]
+    [InlineData("nullTranslations")]
+    [InlineData("nullVariable")]
+    [InlineData("nullTranslation")]
+    [InlineData("missingRequired")]
+    [InlineData("nonBooleanRequired")]
+    [InlineData("duplicateVariable")]
+    [InlineData("blankVariable")]
+    [InlineData("duplicateLanguage")]
+    [InlineData("unknownLanguage")]
+    [InlineData("blankContent")]
+    [InlineData("missingContent")]
+    [InlineData("duplicateRemoval")]
+    [InlineData("unknownRemoval")]
+    [InlineData("nullRemoval")]
+    [InlineData("overlap")]
+    public async Task InvalidUpdateDoesNotChangeContractTranslationsOrRevision(string scenario)
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null, "en", "uk"));
+        var before = await context.ReadAsync();
+        var request = InvalidDefinitionApiBody.Create(scenario, before.GetProperty("revision").GetGuid());
+        var response = await context.UpsertAsync(request);
+        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+        var error = await response.Content.ReadFromJsonAsync<JsonElement>();
+        Assert.False(error.GetProperty("success").GetBoolean());
+        Assert.Equal("InvalidRequest", error.GetProperty("error").GetProperty("code").GetString());
+        Assert.Equal(before.GetRawText(), (await context.ReadAsync()).GetRawText());
+    }
+
+    [Fact]
+    public async Task ConcurrentCreatesAndUpdatesHaveOneWinnerAndNoLostMerge()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var created = await Task.WhenAll(context.UpsertAsync(DefinitionApiTestContext.Body(null, "en")), context.UpsertAsync(DefinitionApiTestContext.Body(null, "uk")));
+        Assert.Equal(new[] { HttpStatusCode.Created, HttpStatusCode.Conflict }, created.Select(r => r.StatusCode).Order().ToArray());
+        var before = await context.ReadAsync();
+        var revision = before.GetProperty("revision").GetGuid();
+        var responses = await Task.WhenAll(context.UpsertAsync(DefinitionApiTestContext.Body(revision, "de")), context.UpsertAsync(DefinitionApiTestContext.Body(revision, "ru")));
+        Assert.Equal(new[] { HttpStatusCode.OK, HttpStatusCode.Conflict }, responses.Select(r => r.StatusCode).Order().ToArray());
+        var after = await context.ReadAsync();
+        Assert.Equal(2, after.GetProperty("translations").GetArrayLength());
+        var retained = before.GetProperty("translations")[0];
+        Assert.Contains(after.GetProperty("translations").EnumerateArray(), item => item.GetProperty("id").GetGuid() == retained.GetProperty("id").GetGuid());
+    }
+
+    [Fact]
+    public async Task RejectedCreateAndMalformedRequestsLeaveNoDefinition()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var definitions = context.ServiceRoot + "/email-template-definitions";
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.Client.GetAsync(definitions)).StatusCode);
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.Client.PostAsJsonAsync(definitions + "/upsert", DefinitionApiTestContext.Body(null))).StatusCode);
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.Client.GetAsync(definitions + "?key=%20")).StatusCode);
+        var invalid = DefinitionApiTestContext.Body(null, "en", "unknown");
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.UpsertAsync(invalid)).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync(context.DefinitionUrl())).StatusCode);
+        using var nullBody = new StringContent("null", System.Text.Encoding.UTF8, "application/json");
+        var response = await context.Client.PostAsync(context.DefinitionUrl(upsert: true), nullBody);
+        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+        Assert.Equal("InvalidRequest", (await response.Content.ReadFromJsonAsync<JsonElement>()).GetProperty("error").GetProperty("code").GetString());
+        var invalidRevision = DefinitionApiTestContext.Body(null);
+        invalidRevision["revision"] = "not-a-guid";
+        Assert.Equal(HttpStatusCode.BadRequest, (await context.UpsertAsync(invalidRevision)).StatusCode);
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync(context.DefinitionUrl())).StatusCode);
+    }
+
+    [Fact]
+    public async Task ExactCaseCatalogCodesCanCoexistAndBeRemovedIndependently()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        using var scope = context.App.Services.CreateScope();
+        var services = scope.ServiceProvider.GetRequiredService<INotificationServiceRepository>();
+        var service = (await services.GetAsync(context.ServiceId))!;
+        service.Languages = service.Languages.Append(new() { Code = "RU" }).ToList();
+        await services.SaveAsync(service, false);
+        Assert.Equal(HttpStatusCode.Created, (await context.UpsertAsync(DefinitionApiTestContext.Body(null, "RU", "ru", "ru-RU"))).StatusCode);
+        var saved = await context.ReadAsync();
+        var removal = DefinitionApiTestContext.Body(saved.GetProperty("revision").GetGuid());
+        removal["variables"] = new JsonArray();
+        removal["removeLanguageCodes"] = new JsonArray("RU");
+        Assert.Equal(HttpStatusCode.OK, (await context.UpsertAsync(removal)).StatusCode);
+        var after = await context.ReadAsync();
+        Assert.Empty(after.GetProperty("variables").EnumerateArray());
+        Assert.Equal(new[] { "ru", "ru-RU" }, after.GetProperty("translations").EnumerateArray().Select(t => t.GetProperty("languageCode").GetString()));
+    }
+
+    [Fact]
+    public async Task LegacyContentWriteInvalidatesLastReadRevision()
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        await context.UpsertAsync(DefinitionApiTestContext.Body(null, "en"));
+        var before = await context.ReadAsync();
+        var body = DefinitionApiTestContext.Body(null, "en");
+        var legacy = (JsonObject)body["translations"]![0]!.DeepClone();
+        legacy["subject"] = "Legacy edit";
+        legacy["variables"] = body["variables"]!.DeepClone();
+        Assert.Equal(HttpStatusCode.OK, (await context.Client.PutAsJsonAsync("/api/v1/email-templates/TestService/Welcome/en", legacy)).StatusCode);
+        Assert.Equal(HttpStatusCode.Conflict, (await context.UpsertAsync(DefinitionApiTestContext.Body(before.GetProperty("revision").GetGuid(), "uk"))).StatusCode);
+        var after = await context.ReadAsync();
+        Assert.Single(after.GetProperty("translations").EnumerateArray());
+        Assert.Equal("Legacy edit", after.GetProperty("translations")[0].GetProperty("subject").GetString());
+    }
+
+    [Theory]
+    [InlineData("Welcome + % # ? Привіт")]
+    [InlineData("Welcome%2Fexact")]
+    [InlineData("Welcome/child")]
+    public async Task EncodedKeysRoundTripExactly(string key)
+    {
+        await using var context = await DefinitionApiTestContext.CreateAsync(fixture);
+        var created = await context.UpsertAsync(DefinitionApiTestContext.Body(null, "ru", "ru-RU"), key);
+        Assert.Equal(HttpStatusCode.Created, created.StatusCode);
+        Assert.NotNull(created.Headers.Location);
+        var located = await context.Client.GetFromJsonAsync<JsonElement>(created.Headers.Location);
+        Assert.Equal(key, located.GetProperty("data").GetProperty("key").GetString());
+        Assert.Equal(context.ServiceId, located.GetProperty("data").GetProperty("serviceId").GetGuid());
+        var read = await context.ReadAsync(key);
+        Assert.Equal(read.GetProperty("id").GetGuid(), located.GetProperty("data").GetProperty("id").GetGuid());
+        Assert.Equal(key, read.GetProperty("key").GetString());
+        Assert.Equal(new[] { "ru", "ru-RU" }, read.GetProperty("translations").EnumerateArray().Select(t => t.GetProperty("languageCode").GetString()));
+        Assert.Equal(HttpStatusCode.NotFound, (await context.Client.GetAsync(context.DefinitionUrl(key.ToLowerInvariant()))).StatusCode);
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/EmailTemplateMigrationTests.cs

@@ -0,0 +1,106 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.Extensions.DependencyInjection;
+using Npgsql;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class EmailTemplateMigrationTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task EquivalentContracts_PreserveLanguageIdsContentAndSharedVariables_AndRerunSafely()
+    {
+        var connection = await fixture.CreateDatabaseAsync(legacy: true);
+        var en = await TemplateDatabaseFixture.InsertLegacyAsync(connection, "en", """[{"name":"Name","required":true},{"name":"Link","required":false}]""");
+        var uk = await TemplateDatabaseFixture.InsertLegacyAsync(connection, "UK", """[{"required":false,"name":"Link"},{"required":true,"name":"Name"}]""");
+        await MigrateAsync(connection);
+        await MigrateAsync(connection);
+        using var services = new ServiceCollection().AddNotificationDataAccess(connection).BuildServiceProvider();
+        using var scope = services.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<IEmailTemplateRepository>();
+        var templates = await repository.GetAllAsync("TestService", "Welcome");
+        Assert.Equal(2, templates.Count);
+        Assert.Contains(templates, t => t.Id == en && t.Subject == "Subject en" && t.HtmlBody == "<p>{{Name}}</p>");
+        Assert.Contains(templates, t => t.Id == uk && t.LanguageCode == "UK" && t.Subject == "Subject UK");
+        Assert.All(templates, t => Assert.Equal(2, t.Variables.Count));
+        await using var db = TemplateDatabaseFixture.CreateContext(connection);
+        await db.GetService<IMigrator>().MigrateAsync(TemplateDatabaseFixture.LegacyMigration);
+        await db.Database.MigrateAsync();
+        Assert.Equal(en, (await repository.GetAsync("TestService", "Welcome", "en"))!.Id);
+    }
+
+    [Theory]
+    [InlineData("[{\"name\":\"Other\",\"required\":true}]", "Conflicting shared variables")]
+    [InlineData("{}", "Invalid template identity or variables array")]
+    [InlineData("[null]", "Invalid variables shape")]
+    [InlineData("[{\"name\":\"Name\",\"required\":\"yes\"}]", "Invalid variables shape")]
+    [InlineData("[{\"name\":\"Name\",\"required\":true},{\"name\":\"Name\",\"required\":true}]", "Duplicate variable names")]
+    public async Task InvalidLegacyData_StopsWithoutChangingSource_ThenCanRecover(string variables, string diagnostic)
+    {
+        var connection = await fixture.CreateDatabaseAsync(legacy: true);
+        await TemplateDatabaseFixture.InsertLegacyAsync(connection, "en", """[{"name":"Name","required":true}]""");
+        await TemplateDatabaseFixture.InsertLegacyAsync(connection, "uk", variables);
+        var error = await Assert.ThrowsAsync<PostgresException>(() => MigrateAsync(connection));
+        Assert.Contains(diagnostic, error.MessageText);
+        Assert.Contains("TestService", error.MessageText);
+        Assert.DoesNotContain("Hello", error.MessageText);
+        await TemplateDatabaseFixture.ExecuteAsync(connection, """
+            DO $$ BEGIN
+                IF to_regclass('public.services') IS NOT NULL OR (SELECT count(*) FROM email_templates) <> 2 THEN
+                    RAISE EXCEPTION 'Migration partially changed source';
+                END IF;
+            END $$;
+            UPDATE email_templates SET variables = '[{"name":"Name","required":true}]'::jsonb;
+            """);
+        await MigrateAsync(connection);
+    }
+
+    [Fact]
+    public async Task ExactLanguageCodes_RemainDistinctAfterMigration()
+    {
+        var connection = await fixture.CreateDatabaseAsync(legacy: true);
+        await TemplateDatabaseFixture.InsertLegacyAsync(connection, "ru", "[]");
+        await TemplateDatabaseFixture.InsertLegacyAsync(connection, "ru-RU", "[]");
+        await TemplateDatabaseFixture.InsertLegacyAsync(connection, "EN", "[]");
+        await TemplateDatabaseFixture.InsertLegacyAsync(connection, "en", "[]");
+        await MigrateAsync(connection);
+        await TemplateDatabaseFixture.ExecuteAsync(connection, """
+            DO $$ BEGIN
+                IF (SELECT count(*) FROM service_languages) <> 4
+                   OR NOT EXISTS (SELECT 1 FROM service_languages WHERE code = 'ru-RU')
+                   OR NOT EXISTS (SELECT 1 FROM service_languages WHERE code = 'EN') THEN
+                    RAISE EXCEPTION 'Migration changed exact language codes';
+                END IF;
+            END $$;
+            """);
+    }
+
+    [Fact]
+    public async Task InterruptedConversion_RollsBackAndCanBeRetried()
+    {
+        var connectionString = await fixture.CreateDatabaseAsync(legacy: true);
+        await TemplateDatabaseFixture.InsertLegacyAsync(connectionString, "en", "[]");
+        await using var db = TemplateDatabaseFixture.CreateContext(connectionString);
+        var script = db.GetService<IMigrator>().GenerateScript(TemplateDatabaseFixture.LegacyMigration, options: MigrationsSqlGenerationOptions.NoTransactions);
+        script = script.Replace("ALTER TABLE email_templates DROP COLUMN", "PERFORM pg_sleep(2); ALTER TABLE email_templates DROP COLUMN");
+        await using (var connection = new NpgsqlConnection(connectionString))
+        {
+            await connection.OpenAsync();
+            await using var transaction = await connection.BeginTransactionAsync();
+            await using var command = new NpgsqlCommand("SET LOCAL statement_timeout = '500ms'; " + script, connection, transaction);
+            var error = await Assert.ThrowsAsync<PostgresException>(() => command.ExecuteNonQueryAsync());
+            Assert.Equal("57014", error.SqlState);
+            await transaction.RollbackAsync();
+        }
+        await MigrateAsync(connectionString);
+    }
+
+    private static async Task MigrateAsync(string connectionString)
+    {
+        await using var db = TemplateDatabaseFixture.CreateContext(connectionString);
+        await db.Database.MigrateAsync();
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/FailingEmailTemplateDefinitionRepository.cs

@@ -0,0 +1,28 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class FailingEmailTemplateDefinitionRepository(IEmailTemplateRepository inner) : IEmailTemplateDefinitionRepository
+{
+    public Task<IReadOnlyList<EmailTemplateDefinition>> GetDefinitionsAsync(string? serviceName = null, string? key = null, CancellationToken ct = default) =>
+        ((IEmailTemplateDefinitionRepository)inner).GetDefinitionsAsync(serviceName, key, ct);
+
+    public Task<EmailTemplateDefinition?> GetDefinitionAsync(string serviceName, string key, CancellationToken ct = default) =>
+        ((IEmailTemplateDefinitionRepository)inner).GetDefinitionAsync(serviceName, key, ct);
+
+    public Task<EmailTemplateDefinition?> GetDefinitionAsync(Guid serviceId, string key, CancellationToken ct = default) =>
+        ((IEmailTemplateDefinitionRepository)inner).GetDefinitionAsync(serviceId, key, ct);
+
+    public Task<EmailTemplateDefinition?> UpsertDefinitionAsync(EmailTemplateDefinitionPatch patch, CancellationToken ct = default) =>
+        throw new IOException("Simulated save failure.");
+
+    public Task<IReadOnlyList<EmailTemplateDefinition>> GetDefinitionsAsync(Guid serviceId, CancellationToken ct = default) =>
+        ((IEmailTemplateDefinitionRepository)inner).GetDefinitionsAsync(serviceId, ct);
+
+    public Task<bool> DeleteDefinitionAsync(Guid serviceId, string key, Guid revision, CancellationToken ct = default) =>
+        ((IEmailTemplateDefinitionRepository)inner).DeleteDefinitionAsync(serviceId, key, revision, ct);
+
+    public Task SaveDefinitionAsync(EmailTemplateDefinition definition, bool isNew, CancellationToken ct = default) =>
+        throw new IOException("Simulated save failure.");
+}

HrynCo.NotificationService.Web.IntegrationTests/HrynCo.NotificationService.Web.IntegrationTests.csproj

@@ -10,16 +10,22 @@
   <ItemGroup>
     <PackageReference Include="coverlet.collector" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
+    <PackageReference Include="Testcontainers.PostgreSql" />
+    <PackageReference Include="SSH.NET" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" />
     <PackageReference Include="xunit" />
     <PackageReference Include="xunit.runner.visualstudio" />
   </ItemGroup>
 
   <ItemGroup>
     <Using Include="Xunit" />
+    <None Include="..\HrynCo.NotificationService.Web\Views\AdminTemplates\Index.cshtml"
+          Link="TestViews\Index.cshtml" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
   <ItemGroup>
     <ProjectReference Include="..\HrynCo.NotificationService.Web\HrynCo.NotificationService.Web.csproj" />
+    <ProjectReference Include="..\HrynCo.NotificationService.Worker.Services\HrynCo.NotificationService.Worker.Services.csproj" />
   </ItemGroup>
 
 </Project>

HrynCo.NotificationService.Web.IntegrationTests/InterimEmailTemplateFixture.cs

@@ -0,0 +1,41 @@
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public static class InterimEmailTemplateFixture
+{
+    public const string MigrationId = "20261017070315_EmailTemplateLocalizations";
+
+    public static async Task<string> CreateAsync(TemplateDatabaseFixture fixture)
+    {
+        var connection = await fixture.CreateDatabaseAsync(legacy: true);
+        await TemplateDatabaseFixture.ExecuteAsync(connection, """
+            DROP INDEX "IX_email_templates_service_name_key_language_code";
+            ALTER TABLE email_templates DROP COLUMN service_name, DROP COLUMN key, DROP COLUMN variables;
+            ALTER TABLE email_templates ADD COLUMN definition_id uuid NOT NULL;
+            CREATE TABLE services (id uuid PRIMARY KEY, name varchar(100) NOT NULL, created timestamptz NOT NULL, updated timestamptz);
+            CREATE UNIQUE INDEX "IX_services_name" ON services(name);
+            CREATE TABLE email_template_definitions (
+                id uuid PRIMARY KEY, service_id uuid NOT NULL REFERENCES services(id) ON DELETE RESTRICT,
+                key varchar(100) NOT NULL, revision uuid NOT NULL, variables jsonb NOT NULL,
+                created timestamptz NOT NULL, updated timestamptz);
+            CREATE UNIQUE INDEX "IX_email_template_definitions_service_id_key" ON email_template_definitions(service_id, key);
+            ALTER TABLE email_templates ADD CONSTRAINT "FK_email_templates_email_template_definitions_definition_id"
+                FOREIGN KEY(definition_id) REFERENCES email_template_definitions(id) ON DELETE CASCADE;
+            CREATE UNIQUE INDEX "IX_email_templates_definition_id_language_code" ON email_templates(definition_id, language_code);
+            INSERT INTO "__EFMigrationsHistory" VALUES ('20261017070315_EmailTemplateLocalizations', '10.0.7');
+            INSERT INTO services VALUES
+                ('11111111-1111-1111-1111-111111111111', 'InterimService', '2026-01-01Z', '2026-02-01Z'),
+                ('88888888-8888-8888-8888-888888888888', 'UnusedService', '2026-01-02Z', null);
+            INSERT INTO email_template_definitions VALUES
+                ('22222222-2222-2222-2222-222222222222', '11111111-1111-1111-1111-111111111111', 'Welcome',
+                    '44444444-4444-4444-4444-444444444444', '[{"name":"Name","required":true}]', '2026-01-03Z', '2026-02-03Z'),
+                ('33333333-3333-3333-3333-333333333333', '11111111-1111-1111-1111-111111111111', 'Empty',
+                    '55555555-5555-5555-5555-555555555555', '[]', '2026-01-04Z', null);
+            INSERT INTO email_templates(id, definition_id, language_code, subject, html_body, text_body, created, updated) VALUES
+                ('66666666-6666-6666-6666-666666666666', '22222222-2222-2222-2222-222222222222', 'ru-RU',
+                    'Hello {{Name}}', '<p>{{Name}}</p>', 'Hello {{Name}}', '2026-01-05Z', '2026-02-05Z'),
+                ('77777777-7777-7777-7777-777777777777', '22222222-2222-2222-2222-222222222222', 'ru',
+                    'Welcome {{Name}}', '<p>Welcome {{Name}}</p>', 'Welcome {{Name}}', '2026-01-06Z', null);
+            """);
+        return connection;
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/InterimEmailTemplateMigrationTests.cs

@@ -0,0 +1,131 @@
+using HrynCo.NotificationService.DAL.Abstract.Repositories;
+using HrynCo.NotificationService.DAL.EF;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.Extensions.DependencyInjection;
+using Npgsql;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public sealed class InterimEmailTemplateMigrationTests(TemplateDatabaseFixture fixture) : IClassFixture<TemplateDatabaseFixture>
+{
+    [Fact]
+    public async Task KnownInterimLayout_UpgradesInPlacePreservingEveryExistingFieldAndHistory()
+    {
+        var connection = await InterimEmailTemplateFixture.CreateAsync(fixture);
+        var original = await SourceSnapshotAsync(connection, upgraded: false);
+        await MigrateAsync(connection);
+        Assert.Equal(original, await SourceSnapshotAsync(connection, upgraded: true));
+        var firstServices = await ScalarAsync(connection, "SELECT jsonb_agg(to_jsonb(s) ORDER BY id)::text FROM services s");
+        await MigrateAsync(connection);
+        Assert.Equal(firstServices, await ScalarAsync(connection, "SELECT jsonb_agg(to_jsonb(s) ORDER BY id)::text FROM services s"));
+        await using var db = TemplateDatabaseFixture.CreateContext(connection);
+        var history = (await db.Database.GetAppliedMigrationsAsync()).ToList();
+        Assert.Equal(4, history.Count);
+        Assert.Contains(InterimEmailTemplateFixture.MigrationId, history);
+        using var provider = new ServiceCollection().AddNotificationDataAccess(connection).BuildServiceProvider();
+        using var scope = provider.CreateScope();
+        var repository = scope.ServiceProvider.GetRequiredService<IEmailTemplateRepository>();
+        Assert.Equal(Guid.Parse("66666666-6666-6666-6666-666666666666"), (await repository.GetAsync("InterimService", "Welcome", "ru-RU"))!.Id);
+        Assert.Equal(Guid.Parse("77777777-7777-7777-7777-777777777777"), (await repository.GetAsync("InterimService", "Welcome", "ru"))!.Id);
+        var definitions = scope.ServiceProvider.GetRequiredService<IEmailTemplateDefinitionRepository>();
+        Assert.Empty((await definitions.GetDefinitionAsync("InterimService", "Empty"))!.Languages);
+        var services = await scope.ServiceProvider.GetRequiredService<INotificationServiceRepository>().GetAllAsync();
+        Assert.Contains(services, s => s.Name == "UnusedService" && s.Languages.Count == 0);
+        Assert.All(services, s => Assert.NotEqual(Guid.Empty, s.Revision));
+    }
+
+    [Theory]
+    [InlineData("ALTER TABLE email_templates ADD COLUMN service_name varchar(100)")]
+    [InlineData("ALTER TABLE email_templates ALTER COLUMN language_code TYPE varchar(11)")]
+    [InlineData("DROP INDEX \"IX_email_templates_definition_id_language_code\"")]
+    [InlineData("DROP INDEX \"IX_email_templates_definition_id_language_code\"; CREATE UNIQUE INDEX \"IX_email_templates_definition_id_language_code\" ON email_templates(id)")]
+    [InlineData("ALTER TABLE email_templates DROP CONSTRAINT \"FK_email_templates_email_template_definitions_definition_id\"; ALTER TABLE email_templates ADD CONSTRAINT \"FK_email_templates_email_template_definitions_definition_id\" FOREIGN KEY(definition_id) REFERENCES email_template_definitions(id) ON DELETE RESTRICT")]
+    [InlineData("DELETE FROM \"__EFMigrationsHistory\" WHERE \"MigrationId\" = '20261017070315_EmailTemplateLocalizations'")]
+    [InlineData("CREATE TABLE service_languages(id uuid)")]
+    public async Task HybridOrUnknownLayout_FailsWithoutAdoptingOrChangingIt(string change)
+    {
+        var connection = await InterimEmailTemplateFixture.CreateAsync(fixture);
+        await TemplateDatabaseFixture.ExecuteAsync(connection, change);
+        var original = await SourceSnapshotAsync(connection, upgraded: false);
+        var error = await Assert.ThrowsAsync<PostgresException>(() => MigrateAsync(connection));
+        Assert.Contains("Unsupported email-template source layout", error.MessageText);
+        Assert.Equal(original, await SourceSnapshotAsync(connection, upgraded: false));
+    }
+
+    [Theory]
+    [InlineData("UPDATE email_template_definitions SET variables = '{}'", "Invalid interim shared variables array")]
+    [InlineData("UPDATE email_template_definitions SET variables = '[null]'", "Invalid interim shared variables shape")]
+    [InlineData("UPDATE email_templates SET language_code = '' WHERE id = '66666666-6666-6666-6666-666666666666'", "Invalid blank identity")]
+    public async Task InvalidInterimData_FailsBeforeSchemaChanges(string change, string diagnostic)
+    {
+        var connection = await InterimEmailTemplateFixture.CreateAsync(fixture);
+        await TemplateDatabaseFixture.ExecuteAsync(connection, change);
+        var original = await SourceSnapshotAsync(connection, upgraded: false);
+        var error = await Assert.ThrowsAsync<PostgresException>(() => MigrateAsync(connection));
+        Assert.Contains(diagnostic, error.MessageText);
+        Assert.Equal(original, await SourceSnapshotAsync(connection, upgraded: false));
+        Assert.Equal("0", await ScalarAsync(connection, "SELECT count(*)::text FROM information_schema.columns WHERE table_name = 'services' AND column_name = 'revision'"));
+    }
+
+    [Fact]
+    public async Task InterruptedInterimUpgrade_RollsBackAndCanBeRetried()
+    {
+        var connectionString = await InterimEmailTemplateFixture.CreateAsync(fixture);
+        var original = await SourceSnapshotAsync(connectionString, upgraded: false);
+        await using var db = TemplateDatabaseFixture.CreateContext(connectionString);
+        var script = db.GetService<IMigrator>().GenerateScript(TemplateDatabaseFixture.LegacyMigration, options: MigrationsSqlGenerationOptions.NoTransactions);
+        script = script.Replace("ALTER TABLE email_templates DROP COLUMN language_code;", "PERFORM pg_sleep(2); ALTER TABLE email_templates DROP COLUMN language_code;");
+        await using (var connection = new NpgsqlConnection(connectionString))
+        {
+            await connection.OpenAsync();
+            await using var transaction = await connection.BeginTransactionAsync();
+            await using var command = new NpgsqlCommand("SET LOCAL statement_timeout = '500ms'; " + script, connection, transaction);
+            Assert.Equal("57014", (await Assert.ThrowsAsync<PostgresException>(() => command.ExecuteNonQueryAsync())).SqlState);
+            await transaction.RollbackAsync();
+        }
+        Assert.Equal(original, await SourceSnapshotAsync(connectionString, upgraded: false));
+        await MigrateAsync(connectionString);
+        Assert.Equal(original, await SourceSnapshotAsync(connectionString, upgraded: true));
+    }
+
+    [Fact]
+    public async Task InterimOrigin_DownIsBlockedBeforeAnyChanges()
+    {
+        var connection = await InterimEmailTemplateFixture.CreateAsync(fixture);
+        await MigrateAsync(connection);
+        var original = await SourceSnapshotAsync(connection, upgraded: true);
+        await using var db = TemplateDatabaseFixture.CreateContext(connection);
+        var error = await Assert.ThrowsAsync<PostgresException>(() => db.GetService<IMigrator>().MigrateAsync(TemplateDatabaseFixture.LegacyMigration));
+        Assert.Contains("Cannot downgrade an interim-origin database", error.MessageText);
+        Assert.Equal(original, await SourceSnapshotAsync(connection, upgraded: true));
+    }
+
+    private static async Task MigrateAsync(string connection)
+    {
+        await using var db = TemplateDatabaseFixture.CreateContext(connection);
+        await db.Database.MigrateAsync();
+    }
+
+    private static Task<string> SourceSnapshotAsync(string connection, bool upgraded)
+    {
+        var versions = upgraded
+            ? "SELECT (to_jsonb(t) - 'service_id' - 'service_language_id') || jsonb_build_object('language_code', l.code) AS value FROM email_templates t JOIN service_languages l ON l.id = t.service_language_id"
+            : "SELECT to_jsonb(t) AS value FROM email_templates t";
+        return ScalarAsync(connection, $"""
+            SELECT jsonb_build_object(
+                'services', (SELECT jsonb_agg(to_jsonb(s) - 'revision' ORDER BY id) FROM services s),
+                'definitions', (SELECT jsonb_agg(to_jsonb(d) ORDER BY id) FROM email_template_definitions d),
+                'versions', (SELECT jsonb_agg(value ORDER BY value->>'id') FROM ({versions}) q))::text
+            """);
+    }
+
+    private static async Task<string> ScalarAsync(string connectionString, string sql)
+    {
+        await using var connection = new NpgsqlConnection(connectionString);
+        await connection.OpenAsync();
+        await using var command = new NpgsqlCommand(sql, connection);
+        return (string)(await command.ExecuteScalarAsync())!;
+    }
+}

HrynCo.NotificationService.Web.IntegrationTests/InvalidDefinitionApiBody.cs

@@ -0,0 +1,47 @@
+using System.Text.Json.Nodes;
+
+namespace HrynCo.NotificationService.Web.IntegrationTests;
+
+public static class InvalidDefinitionApiBody
+{
+    public static JsonObject Create(string scenario, Guid revision)
+    {
+        var body = DefinitionApiTestContext.Body(revision, "en");
+        body["removeLanguageCodes"] = new JsonArray("uk");
+        ApplyVariableScenario(scenario, body, (JsonArray)body["variables"]!);
+        ApplyTranslationScenario(scenario, body, (JsonArray)body["translations"]!);
+        return body;
+    }
+
+    private static void ApplyVariableScenario(string scenario, JsonObject body, JsonArray variables)
+    {
+        switch (scenario)
+        {
+            case "missingVariables": body.Remove("variables"); break;
+            case "nullVariables": body["variables"] = null; break;
+            case "nullVariable": variables.Add((JsonNode?)null); break;
+            case "missingRequired": ((JsonObject)variables[0]!).Remove("required"); break;
+            case "nonBooleanRequired": variables[0]!["required"] = "true"; break;
+            case "duplicateVariable": variables.Add(variables[0]!.DeepClone()); break;
+            case "blankVariable": variables[0]!["name"] = " "; break;
+        }
+    }
+
+    private static void ApplyTranslationScenario(string scenario, JsonObject body, JsonArray translations)
+    {
+        switch (scenario)
+        {
+            case "missingTranslations": body.Remove("translations"); break;
+            case "nullTranslations": body["translations"] = null; break;
+            case "nullTranslation": translations.Add((JsonNode?)null); break;
+            case "duplicateLanguage": translations.Add(translations[0]!.DeepClone()); break;
+            case "unknownLanguage": translations[0]!["languageCode"] = "RU"; break;
+            case "blankContent": translations[0]!["textBody"] = " "; break;
+            case "missingContent": ((JsonObject)translations[0]!).Remove("htmlBody"); break;
+            case "duplicateRemoval": body["removeLanguageCodes"] = new JsonArray("uk", "uk"); break;
+            case "unknownRemoval": body["removeLanguageCodes"] = new JsonArray("UK"); break;
+            case "nullRemoval": body["removeLanguageCodes"] = new JsonArray((JsonNode?)null); break;
+            case "overlap": body["removeLanguageCodes"] = new JsonArray("en"); break;
+        }
+    }
+}