Refactor email handling for improved structure

Refactored `Email` and `SendingEmailEvent` to use `record` types, consolidating email-related data into the `Email` class. Updated `SendEmailCommand` to return a `Guid` and simplified mapping logic in `EmailMappingProfile`. Adjusted `SendEmailCommandHandler` to construct `SendingEmailEvent` manually.

Updated `SendingEmailConsumer`, `EmailsController`, and `EmailSender` to reflect the new structure. Removed the old `Email` implementation. Improved logging to reference the `Mail` property.

Revised tests to align with the new structure, ensuring immutability and better separation of concerns.

src/presentation/DigitalData.MessagingService.API/Controllers/EmailsController.cs

@@ -23,11 +23,11 @@ public class EmailsController(IMediator mediator) : ControllerBase
     [ProducesResponseType(StatusCodes.Status400BadRequest)]
     public async Task<IActionResult> SendEmail([FromBody] SendEmailCommand command, CancellationToken cancellationToken)
     {
-        var sendingEmailEvent = await mediator.Send(command, cancellationToken);
+        var eventId = await mediator.Send(command, cancellationToken);
 
         return Accepted(new
         {
-            sendingEmailEvent.Id,
+            Id = eventId
         });
     }
 }