feat(templates): add localized push templates and actions

Share template keys across email and push with independent editors and revisions. Render localized actions and preserve version-one delivery.

Ref: IT-1627

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

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+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Repositories;
+
+public interface IPushTemplateDefinitionRepository
+{
+    Task<IReadOnlyList<PushTemplateDefinition>> GetDefinitionsAsync(Guid serviceId, CancellationToken ct = default);
+    Task<PushTemplateDefinition?> GetAsync(Guid serviceId, string key, CancellationToken ct = default);
+    Task SaveAsync(PushTemplateDefinition definition, bool isNew, CancellationToken ct = default);
+    Task<bool> DeleteAsync(Guid serviceId, string key, Guid revision, CancellationToken ct = default);
+}

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

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+using System.Text.Json;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public static class PushTemplateActionValidation
+{
+    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
+    {
+        PropertyNameCaseInsensitive = false
+    };
+
+    public static PushTemplateActions Parse(string json)
+    {
+        if (string.IsNullOrWhiteSpace(json))
+            throw new EmailTemplateWriteException("Actions JSON is required. Use {} for no actions.", false);
+        try
+        {
+            var actions = JsonSerializer.Deserialize<PushTemplateActions>(json, JsonOptions)
+                ?? throw new JsonException();
+            Validate(actions);
+            return actions;
+        }
+        catch (JsonException)
+        {
+            throw new EmailTemplateWriteException("Invalid actions JSON. Use defaultAction and buttons with action and label.", false);
+        }
+    }
+
+    public static void Validate(PushTemplateActions actions)
+    {
+        if (actions.DefaultAction is not null) ValidateKey(actions.DefaultAction);
+        if (actions.Buttons is null || actions.Buttons.Count > 3)
+            throw new EmailTemplateWriteException("Configure up to three push buttons.", false);
+        var keys = new HashSet<string>(StringComparer.Ordinal);
+        foreach (var button in actions.Buttons)
+        {
+            if (button is null) throw new EmailTemplateWriteException("A button needs an action and label.", false);
+            ValidateKey(button.Action);
+            if (!keys.Add(button.Action) || string.IsNullOrWhiteSpace(button.Label) || button.Label.Length > 100)
+                throw new EmailTemplateWriteException("Button actions must be unique and labels must contain 1–100 characters.", false);
+        }
+    }
+
+    private static void ValidateKey(string key)
+    {
+        if (string.IsNullOrWhiteSpace(key) || key.Length > 100 || key.Any(c => !char.IsAsciiLetterOrDigit(c) && c is not '_' and not '-' and not '.'))
+            throw new EmailTemplateWriteException("Action keys need 1–100 letters, digits, dots, underscores or hyphens.", false);
+    }
+}

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

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+using System.Text.Json.Serialization;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+[JsonUnmappedMemberHandling(JsonUnmappedMemberHandling.Disallow)]
+public sealed record PushTemplateActions
+{
+    public string? DefaultAction { get; init; }
+    public IReadOnlyList<PushTemplateButton> Buttons { get; init; } = [];
+}

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

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+using System.Text.Json.Serialization;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+[JsonUnmappedMemberHandling(JsonUnmappedMemberHandling.Disallow)]
+public sealed record PushTemplateButton
+{
+    public required string Action { get; init; }
+    public required string Label { get; init; }
+}

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

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+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class PushTemplateDefinition
+{
+    public Guid Id { get; set; }
+    public Guid ServiceId { get; set; }
+    public required string Key { get; set; }
+    public Guid Revision { get; set; }
+    public IReadOnlyList<EmailTemplateVariable> Variables { get; set; } = [];
+    public IReadOnlyList<PushTemplateTranslation> Languages { get; set; } = [];
+}

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

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+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public sealed class PushTemplateTranslation
+{
+    public string ActionsJson { get; set; } = "{}";
+    public required string LanguageCode { get; set; }
+    public required string Title { get; set; }
+    public required string Body { get; set; }
+}

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

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+using System.Text.RegularExpressions;
+
+namespace HrynCo.NotificationService.DAL.Abstract.Templates;
+
+public static partial class PushTemplateValidation
+{
+    public static void Validate(PushTemplateDefinition definition)
+    {
+        EmailTemplateValidation.ValidateIdentity("Push", definition.Key);
+        EmailTemplateValidation.ValidateVariables(definition.Variables);
+        var names = definition.Variables.Select(v => v.Name).ToHashSet(StringComparer.Ordinal);
+        foreach (var language in definition.Languages)
+            ValidateTranslation(language, names);
+        if (definition.Languages.Select(l => l.LanguageCode).Distinct(StringComparer.Ordinal).Count() != definition.Languages.Count)
+            throw new EmailTemplateWriteException("Language codes must be unique within a template.", false);
+    }
+
+    private static void ValidateTranslation(PushTemplateTranslation translation, HashSet<string> names)
+    {
+        if (string.IsNullOrWhiteSpace(translation.LanguageCode) || translation.LanguageCode.Length > 10)
+            throw new EmailTemplateWriteException("A valid language code is required.", false);
+        if (string.IsNullOrWhiteSpace(translation.Title) || string.IsNullOrWhiteSpace(translation.Body))
+            throw new EmailTemplateWriteException("Every populated push language needs both Title and Body.", false);
+        ValidatePlaceholders(translation.Title, names);
+        ValidatePlaceholders(translation.Body, names);
+        var actions = PushTemplateActionValidation.Parse(translation.ActionsJson);
+        foreach (var button in actions.Buttons) ValidatePlaceholders(button.Label, names);
+    }
+
+    private static void ValidatePlaceholders(string text, HashSet<string> names)
+    {
+        foreach (Match match in Placeholder().Matches(text))
+            if (!names.Contains(match.Groups[1].Value))
+                throw new EmailTemplateWriteException("Every placeholder must be declared in this channel's variables.", false);
+        var remainder = Placeholder().Replace(text, "");
+        if (remainder.Contains("{{", StringComparison.Ordinal) || remainder.Contains("}}", StringComparison.Ordinal))
+            throw new EmailTemplateWriteException("Use complete placeholders in the form {{VariableName}}.", false);
+    }
+
+    [GeneratedRegex(@"\{\{([^{}]+)\}\}")]
+    private static partial Regex Placeholder();
+}