Remove HasAttachments filter; enhance FetchEmails response

The `MailSearchFilter` class was updated to remove the `HasAttachments` property, simplifying the filtering logic. Corresponding client-side filtering logic in `LimilabsImapEmailService` was also removed. The IMAP search query now defaults to `Expression.All` when no criteria are provided.

The `FetchEmails` method in `EmailController` was enhanced with a new optional `firstHtmlBodyOnly` parameter. This allows returning only the HTML body of the first email or a `404 Not Found` response if no emails match the criteria. These changes improve flexibility and simplify the codebase.

src/core/DigitalData.MessagingService.Application/Common/Models/MailSearch/MailSearchFilter.cs

@@ -19,12 +19,6 @@ public record MailSearchFilter
     /// </summary>
     public bool UnseenOnly { get; init; } = false;
 
-    /// <summary>
-    /// When <see langword="true"/>, only messages that carry at least one attachment are returned.
-    /// Filtered client-side after fetching the message envelope; does not affect the IMAP SEARCH query.
-    /// </summary>
-    public bool HasAttachments { get; init; } = false;
-
     /// <summary>
     /// When <see langword="true"/>, attachment data is included in the results; otherwise attachments are omitted.
     /// Defaults to <see langword="false"/>.

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

@@ -78,7 +78,8 @@ public class LimilabsImapEmailService(
             }
 
             // Get UIDs to fetch
-            List<long> uids = [.. await imap.SearchAsync(Expression.And([.. criterions]), cancellationToken)];
+            var searchExpression = criterions.Count > 0 ? Expression.And([.. criterions]) : Expression.All();
+            List<long> uids = [.. await imap.SearchAsync(searchExpression, cancellationToken)];
 
             // Apply requested sort order
             if (filter.SortOrder == MailSortOrder.NewestFirst)
@@ -99,10 +100,6 @@ public class LimilabsImapEmailService(
                     var mail  = new MailBuilder().CreateFromEml(eml);
                     var flags = await imap.GetFlagsByUIDAsync(uid, cancellationToken);
 
-                    // Client-side attachment filter — IMAP has no native criterion for this
-                    if (filter.HasAttachments && mail.Attachments.Count == 0 && mail.Visuals.Count == 0)
-                        continue;
-
                     results.Add(MapToContext(uid, mail, flags, filter.WithAttachments));
                 }
                 catch (Exception ex)

src/presentation/DigitalData.MessagingService.API/Controllers/EmailController.cs

@@ -78,9 +78,16 @@ public class EmailController(IMediator mediator) : ControllerBase
     [ProducesResponseType(StatusCodes.Status200OK)]
     [ProducesResponseType(StatusCodes.Status400BadRequest)]
     [ProducesResponseType(StatusCodes.Status404NotFound)]
-    public async Task<IActionResult> FetchEmails([FromQuery] FetchEmailsQuery query, CancellationToken cancellationToken = default)
+    public async Task<IActionResult> FetchEmails([FromQuery] FetchEmailsQuery query, [FromQuery] bool firstHtmlBodyOnly = false, CancellationToken cancellationToken = default)
     {
         var emails = await mediator.Send(query, cancellationToken);
+
+        if(!emails.Any())
+            return NotFound("No emails found matching the specified criteria.");
+
+        if (firstHtmlBodyOnly && emails.FirstOrDefault()?.HtmlBody is string htmlBody)
+            return Ok(htmlBody);
+
         return Ok(emails);
     }