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.

tests/DigitalData.MessagingService.Tests/Integration/SendingEmailPublisherTests.cs

@@ -37,10 +37,14 @@ public sealed class SendingEmailPublisherTests : IAsyncDisposable
         var email = new SendingEmailEvent
         {
             Id = Guid.NewGuid(),
-            Recipients = ["test@example.com"],
-            Subject = "Integration Test - EnqueueAsync",
-            Body = "<p>Hello from integration test.</p>",
-            IsHtml = true,
+            Mail = new Email
+            {
+                Sender = new EmailAccountDto { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = ["test@example.com"],
+                Subject = "Integration Test - EnqueueAsync",
+                Body = "<p>Hello from integration test.</p>",
+                IsHtml = true,
+            },
             QueuedAt = DateTime.Now
         };
 
@@ -62,10 +66,14 @@ public sealed class SendingEmailPublisherTests : IAsyncDisposable
         var emails = Enumerable.Range(1, 3).Select(i => new SendingEmailEvent
         {
             Id = Guid.NewGuid(),
-            Recipients = new List<string> { $"recipient{i}@example.com" },
-            Subject = $"Integration Test - Batch #{i}",
-            Body = $"Batch message {i}",
-            IsHtml = false,
+            Mail = new Email
+            {
+                Sender = new EmailAccountDto { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = new List<string> { $"recipient{i}@example.com" },
+                Subject = $"Integration Test - Batch #{i}",
+                Body = $"Batch message {i}",
+                IsHtml = false,
+            },
             QueuedAt = DateTime.Now
         }).ToList();
 
@@ -85,10 +93,14 @@ public sealed class SendingEmailPublisherTests : IAsyncDisposable
         var email = new SendingEmailEvent
         {
             Id = Guid.NewGuid(),
-            Recipients = ["depth-test@example.com"],
-            Subject = "Integration Test - GetQueueDepth",
-            Body = "Queue depth test",
-            IsHtml = false,
+            Mail = new Email
+            {
+                Sender = new EmailAccountDto { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = ["depth-test@example.com"],
+                Subject = "Integration Test - GetQueueDepth",
+                Body = "Queue depth test",
+                IsHtml = false,
+            },
             QueuedAt = DateTime.Now
         };
 
@@ -108,10 +120,14 @@ public sealed class SendingEmailPublisherTests : IAsyncDisposable
         var email = new SendingEmailEvent
         {
             Id = id,
-            Recipients = new List<string> { "serialize@example.com" },
-            Subject = "Serialization Test",
-            Body = "<strong>Bold</strong>",
-            IsHtml = true,
+            Mail = new Email
+            {
+                Sender = new EmailAccountDto { Username = "test@example.com", Password = "password", SmtpServer = "smtp.example.com" },
+                Recipients = new List<string> { "serialize@example.com" },
+                Subject = "Serialization Test",
+                Body = "<strong>Bold</strong>",
+                IsHtml = true,
+            },
             QueuedAt = DateTime.Now
         };
 
@@ -123,10 +139,10 @@ public sealed class SendingEmailPublisherTests : IAsyncDisposable
 
         Assert.NotNull(received);
         Assert.Equal(id, received.Id);
-        Assert.Equal(["serialize@example.com"], received.Recipients);
-        Assert.Equal("Serialization Test", received.Subject);
-        Assert.Equal("<strong>Bold</strong>", received.Body);
-        Assert.True(received.IsHtml);
+        Assert.Equal(["serialize@example.com"], received.Mail.Recipients);
+        Assert.Equal("Serialization Test", received.Mail.Subject);
+        Assert.Equal("<strong>Bold</strong>", received.Mail.Body);
+        Assert.True(received.Mail.IsHtml);
     }
 
     /// <summary>