Refactor SendAsync method in MessagingServiceClient

The `SendAsync` method in the `MessagingServiceClient` class has been refactored. It no longer uses the `async` keyword and instead directly returns the `Task` from `sender.Send`. This change simplifies the method by removing the `await` operation, while still maintaining asynchronous behavior through the returned `Task`.

src/presentation/DigitalData.MessagingService.Client/MessagingServiceClient.cs

@@ -16,9 +16,9 @@ public class MessagingServiceClient(ISender sender)
     /// <param name="email"></param>
     /// <param name="cancellationToken"></param>
     /// <returns></returns>
-    public async Task SendAsync(Email email, CancellationToken cancellationToken = default)
+    public Task SendAsync(Email email, CancellationToken cancellationToken = default)
     {
-        await sender.Send(new PublishEmailViaSmtpCommand()
+        return sender.Send(new PublishEmailViaSmtpCommand()
         {
             Sender = new GetEmailAccountQuery()
             {