added guardian letters with chat and multiple answer functionalities

lib/api/marianumconnect/queries/get_newsletter_file/get_newsletter_file.dart

@@ -1,7 +1,5 @@
 import 'dart:typed_data';
 
-import 'package:dio/dio.dart';
-
 import '../../marianumconnect_query.dart';
 
 /// Downloads the raw PDF bytes of a Marianum Message from
@@ -15,11 +13,6 @@ class GetNewsletterFile extends MarianumConnectQuery {
 
   GetNewsletterFile(this.id, {super.dio});
 
-  Future<Uint8List> run() => guard(() async {
-    final response = await dio.get<List<int>>(
-      endpoint('newsletter/${Uri.encodeComponent(id)}/file'),
-      options: Options(responseType: ResponseType.bytes),
-    );
-    return Uint8List.fromList(response.data!);
-  });
+  Future<Uint8List> run() =>
+      getBytes('newsletter/${Uri.encodeComponent(id)}/file');
 }