Refactor: Remove IOutgoingEmailConsumer interface

Simplified the codebase by removing the `IOutgoingEmailConsumer` interface and directly using the `OutgoingEmailConsumer` class.

- Removed `IOutgoingEmailConsumer` from the application.
- Updated `DependencyInjection` to register `OutgoingEmailConsumer` directly.
- Modified `OutgoingEmailConsumer` to no longer implement the removed interface.
- Updated `AsyncInitWorker` to depend directly on `OutgoingEmailConsumer`.
- Simplified initialization logic for email consumer and publisher.

These changes eliminate an unnecessary abstraction layer, making the code easier to maintain while preserving functionality.

src/DigitalData.MessagingService.Application/Common/Interfaces/IOutgoingEmailConsumer.cs

@@ -1,8 +0,0 @@
-namespace DigitalData.MessagingService.Application.Common.Interfaces;
-
-/// <summary>
-/// Email queue interface for outgoing emails.
-/// </summary>
-public interface IOutgoingEmailConsumer
-{
-}