feat(templates): add service language template management

Add normalized service and template catalogs, scoped administration, migration, validation, and regression coverage.

Ref: IT-1601

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);
 
-        await _templates.DeleteAsync(template, cancellationToken);
+        try
+        {
+            await _templates.DeleteAsync(template, cancellationToken);
+        }
+        catch (EmailTemplateWriteException error)
+        {
+            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
+        }
 
         return Success(Unit.Value);
     }