feat: capture development email in MailHog via the Aspire sample (#73)

samples/AndreGoepel.AppFoundation.AppHost/AppHost.cs

@@ -7,10 +7,29 @@
 // (AppFoundationOptions.DatabaseConnectionName == "appfoundation-database").
 var database = postgres.AddDatabase("appfoundation-database", "appfoundation");
 
+// MailHog captures outgoing development email locally: an SMTP server on 1025 and a web UI on
+// 8025 to read what was "sent". Nothing leaves the machine, and no real mail account is needed.
+var mailhog = builder
+    .AddContainer("mailhog", "mailhog/mailhog", "v1.0.1")
+    .WithEndpoint(name: "smtp", port: 1025, targetPort: 1025)
+    .WithHttpEndpoint(name: "http", port: 8025, targetPort: 8025);
+
 // The sample web app, wired to the database and started only once it is ready.
 builder
     .AddProject<Projects.AndreGoepel_AppFoundation_Sample>("web")
     .WithReference(database)
-    .WaitFor(database);
+    .WaitFor(database)
+    .WaitFor(mailhog)
+    // Pre-configure the EmailSender bootstrap section to send through MailHog. These values
+    // come from configuration rather than the database, so email keeps working after a
+    // database reset with no manual setup on the Email Settings page. MailHog needs no
+    // credentials, but the settings are required, so placeholders are supplied.
+    .WithEnvironment("EmailSender__SenderName", "AppFoundation Dev")
+    .WithEnvironment("EmailSender__SenderEmail", "dev@appfoundation.local")
+    .WithEnvironment("EmailSender__Server", "localhost")
+    .WithEnvironment("EmailSender__Port", "1025")
+    .WithEnvironment("EmailSender__UseSsl", "false")
+    .WithEnvironment("EmailSender__Username", "dev")
+    .WithEnvironment("EmailSender__Password", "dev");
 
 builder.Build().Run();

src/AndreGoepel.AppFoundation.MailService/SmtpEmailSender.cs

@@ -37,11 +37,23 @@ await client.ConnectAsync(
             configuration.UseSsl,
             cancellationToken
         );
-        await client.AuthenticateAsync(
-            configuration.Username,
-            configuration.Password,
-            cancellationToken
-        );
+
+        // Only authenticate when the server offers it and credentials are configured.
+        // Development relays such as MailHog accept mail without authentication and don't
+        // advertise AUTH, and MailKit throws if AuthenticateAsync is called against such a
+        // server.
+        if (
+            client.Capabilities.HasFlag(SmtpCapabilities.Authentication)
+            && !string.IsNullOrEmpty(configuration.Username)
+        )
+        {
+            await client.AuthenticateAsync(
+                configuration.Username,
+                configuration.Password,
+                cancellationToken
+            );
+        }
+
         await client.SendAsync(message, cancellationToken);
         await client.DisconnectAsync(true, cancellationToken);
     }