Refactor LimilabsEmailService for async operations

Modernized LimilabsEmailService by replacing synchronous SMTP
operations with asynchronous counterparts (e.g., SendMessageAsync,
CloseAsync). Introduced a new SmtpExtensions class with a
CloseSafelyAsync method for safe disconnection. Removed the
DisconnectSafely method and replaced its usage with the new
extension method. Improved exception handling and removed
redundant Task.CompletedTask calls. These changes enhance
code readability, ensure safe resource cleanup, and align
with asynchronous programming practices.

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Extensions/SmtpExtensions.cs

@@ -0,0 +1,16 @@
+using Limilabs.Client.SMTP;
+
+namespace DigitalData.MessagingService.Infrastructure.Services.Extensions;
+
+public static class SmtpExtensions
+{
+    public static async Task CloseSafelyAsync(this Smtp smtp)
+    {
+        try
+        {
+            if (smtp.Connected)
+                await smtp.CloseAsync();
+        }
+        catch { /* Ignore disconnect errors */ }
+    }
+}

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/LimilabsEmailService.cs

@@ -7,6 +7,7 @@ using Limilabs.Mail;
 using Limilabs.Mail.Headers;
 using Microsoft.Extensions.Options;
 using DigitalData.MessagingService.Application.Common.Options;
+using DigitalData.MessagingService.Infrastructure.Services.Extensions;
 
 namespace DigitalData.MessagingService.Infrastructure.Services;
 
@@ -53,39 +54,37 @@ public class LimilabsEmailService(
 
             var mail = builder.Create();
 
-            var result = smtp.SendMessage(mail);
+            var result = await smtp.SendMessageAsync(mail, cancellationToken);
 
             if (result.Status != SendMessageStatus.Success)
             {
                 throw new InvalidOperationException($"Failed to send email. Status: {result.Status}");
             }
 
-            smtp.Close();
+            await smtp.CloseAsync(cancellationToken);
             await Task.CompletedTask; // For async consistency
         }
         catch (Limilabs.Client.ServerException ex)
         {
-            DisconnectSafely(smtp);
+            await smtp.CloseSafelyAsync();
             throw new AuthenticationFailedException("SMTP authentication failed. Check credentials or OAuth2 configuration.", ex);
         }
         catch (Exception ex)
         {
-            DisconnectSafely(smtp);
+            await smtp.CloseSafelyAsync();
             throw new InvalidOperationException("Failed to send email via SMTP server.", ex);
         }
     }
 
-    // --- Private Helper Methods ---
-
     private async Task ConnectAndAuthenticateSmtpAsync(Smtp smtp, EmailAccountDto smtpAccount)
     {
         if (smtpAccount.SmtpUseSsl)
         {
-            smtp.ConnectSSL(smtpAccount.SmtpServer, smtpAccount.SmtpPort);
+            await smtp.ConnectSSLAsync(smtpAccount.SmtpServer, smtpAccount.SmtpPort);
         }
         else
         {
-            smtp.Connect(smtpAccount.SmtpServer, smtpAccount.SmtpPort);
+            await smtp.ConnectAsync(smtpAccount.SmtpServer, smtpAccount.SmtpPort);
         }
 
         if (smtpAccount.UseOAuth2)
@@ -96,19 +95,7 @@ public class LimilabsEmailService(
         {
             var password = smtpAccount.PasswordEncrypted ? encryptionService.Decrypt(smtpAccount.Password) : smtpAccount.Password;
 
-            smtp.Login(smtpAccount.Username, password);
+            await smtp.LoginAsync(smtpAccount.Username, password);
         }
-
-        await Task.CompletedTask; // For async consistency
-    }
-
-    private static void DisconnectSafely(Smtp smtp)
-    {
-        try
-        {
-            if (smtp.Connected)
-                smtp.Close();
-        }
-        catch { /* Ignore disconnect errors */ }
     }
 }