Refactor EmailSender to use new Email abstraction

Introduced a new `Email` record to simplify the representation of outgoing email messages. Updated the `EmailSender.Send` method to accept `Email` instead of `OutgoingEmailEvent`, with a `ToEvent()` method handling the conversion internally.

Refactored test cases to use the `Email` record, removing redundant properties (`Id` and `QueuedAt`) that are now auto-generated. Updated XML documentation to reflect these changes. Adjusted namespaces and added necessary `using` directives for proper referencing.

These changes improve code readability, maintainability, and centralize the mapping logic for outgoing email events.

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

@@ -0,0 +1,46 @@
+using DigitalData.MessagingService.Publisher.Abstraction;
+
+namespace DigitalData.MessagingService.Client;
+
+/// <summary>
+/// Represents an outgoing email message to be sent through the messaging service.
+/// </summary>
+public record Email
+{
+    /// <summary>
+    /// Recipient email address
+    /// </summary>
+    public string Recipient { get; set; } = null!;
+
+    /// <summary>
+    /// Email subject
+    /// </summary>
+    public string Subject { get; set; } = null!;
+
+    /// <summary>
+    /// Email body (HTML or plain text)
+    /// </summary>
+    public string Body { get; set; } = null!;
+
+    /// <summary>
+    /// Is HTML email (default: true)
+    /// </summary>
+    public bool IsHtml { get; set; } = true;
+
+    /// <summary>
+    /// Converts this <see cref="Email"/> instance to an <see cref="OutgoingEmailEvent"/>.
+    /// </summary>
+    /// <returns>A new <see cref="OutgoingEmailEvent"/> representing this email.</returns>
+    internal OutgoingEmailEvent ToEvent()
+    {
+        return new OutgoingEmailEvent
+        {
+            Id = Guid.NewGuid(),
+            Recipient = Recipient,
+            Subject = Subject,
+            Body = Body,
+            IsHtml = IsHtml,
+            QueuedAt = DateTime.Now
+        };
+    }
+}

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

@@ -106,24 +106,25 @@ public static class EmailSender
     }
 
     /// <summary>
-    /// Enqueues the specified email event to the RabbitMQ messaging pipeline.
+    /// Enqueues the specified email to the RabbitMQ messaging pipeline.
     /// </summary>
-    /// <param name="email">The outgoing email event to enqueue.</param>
+    /// <param name="email">The outgoing email data to enqueue.</param>
     /// <exception cref="InvalidOperationException">
     /// Thrown when <see cref="ConnectRabbitMq(Action{RabbitMqConfiguration}, OnReconnect)"/> has not been called prior to sending.
     /// </exception>
     /// <remarks>
-    /// This method resolves <see cref="IOutgoingEmailPublisher"/> from the internal
+    /// This method maps <see cref="Email"/> to <see cref="OutgoingEmailEvent"/>,
+    /// then resolves <see cref="IOutgoingEmailPublisher"/> from the internal
     /// service provider and calls <c>EnqueueAsync</c> in a fire-and-forget manner.
     /// Ensure that any unhandled exceptions from the async operation are handled
     /// at the publisher level.
     /// </remarks>
-    public static void Send(OutgoingEmailEvent email)
+    public static void Send(Email email)
     {
         if(!IsConnected)
             throw new InvalidOperationException("Messaging service is not connected. Call ConnectRabbitMq first.");
 
         var publisher = LazyProvider.Value.GetRequiredService<IOutgoingEmailPublisher>();
-        publisher.EnqueueAsync(email);
+        publisher.EnqueueAsync(email.ToEvent());
     }
 }