Refactor: Rename OutgoingEmail to SendingEmail

This commit renames and refactors all instances of `OutgoingEmail` to `SendingEmail` across the codebase to improve terminology consistency and align with domain language.

- Renamed classes, interfaces, and records (e.g., `OutgoingEmailPublisher` → `SendingEmailPublisher`, `OutgoingEmailEvent` → `SendingEmailEvent`).
- Updated method signatures, parameters, and return types to use `SendingEmail`.
- Adjusted dependency injection registrations to reflect the new naming.
- Updated mappings in `EmailMappingProfile` to map `SendEmailCommand` to `SendingEmailEvent`.
- Refactored `SendEmailCommand` and its handler to work with `SendingEmailEvent`.
- Updated `EmailsController` to use `SendingEmailEvent` in the `SendEmail` action.
- Refactored integration tests to test `SendingEmailPublisher` and updated test data accordingly.
- Updated log messages, error handling, and comments to reflect the new terminology.
- Revised documentation and utility methods to use `SendingEmailEvent`.

This refactor ensures consistency, improves readability, and reduces ambiguity in the codebase.

src/infrastructure/DigitalData.MessagingService.Publisher/DependencyInjection.cs

@@ -13,7 +13,7 @@ public static class DependencyInjection
             services.AddRabbitMqConnectionFactory(configure);
 
         // --- Email Queue (RabbitMQ) ---
-        services.AddSingleton<IOutgoingEmailPublisher, OutgoingEmailPublisher>();
+        services.AddSingleton<ISendingEmailPublisher, SendingEmailPublisher>();
 
         return services;
     }

src/infrastructure/DigitalData.MessagingService.Publisher/OutgoingEmailPublisher.cs

@@ -13,14 +13,14 @@ namespace DigitalData.MessagingService.Publisher;
 /// Provides message persistence, scalability, and reliability.
 /// Uses Lazy<T> initialization pattern to avoid blocking constructor.
 /// </summary>
-public sealed class OutgoingEmailPublisher : IOutgoingEmailPublisher, IAsyncDisposable
+public sealed class SendingEmailPublisher : ISendingEmailPublisher, IAsyncDisposable
 {
     private readonly RabbitMqConfiguration _config;
-    private readonly ILogger<OutgoingEmailPublisher> _logger;
+    private readonly ILogger<SendingEmailPublisher> _logger;
     private readonly RabbitMqConnectionFactory _cnnFactory;
     private readonly Lazy<Task<IChannel>> _lazyChannel;
 
-    public OutgoingEmailPublisher(IOptions<RabbitMqConfiguration> config, ILogger<OutgoingEmailPublisher> logger, RabbitMqConnectionFactory cnnFactory)
+    public SendingEmailPublisher(IOptions<RabbitMqConfiguration> config, ILogger<SendingEmailPublisher> logger, RabbitMqConnectionFactory cnnFactory)
     {
         _config = config.Value;
         _logger = logger;
@@ -66,9 +66,9 @@ public sealed class OutgoingEmailPublisher : IOutgoingEmailPublisher, IAsyncDisp
         return channel;
     }
     
-    public async Task EnqueueAsync(OutgoingEmailEvent outgoingEmailEvent, CancellationToken cancellationToken = default)
+    public async Task EnqueueAsync(SendingEmailEvent sendingEmailEvent, CancellationToken cancellationToken = default)
     {
-        var json = JsonSerializer.Serialize(outgoingEmailEvent);
+        var json = JsonSerializer.Serialize(sendingEmailEvent);
         var body = Encoding.UTF8.GetBytes(json);
 
         var properties = new BasicProperties