Added Marianum Message pdf reader and backend

lib/api/mhsl/message/getMessages/getMessagesCache.dart

@@ -0,0 +1,22 @@
+import 'dart:convert';
+
+import 'package:marianum_mobile/api/mhsl/message/getMessages/getMessagesResponse.dart';
+import 'package:marianum_mobile/api/requestCache.dart';
+
+import 'getMessages.dart';
+
+class GetMessagesCache extends RequestCache<GetMessagesResponse> {
+  GetMessagesCache({onUpdate, renew}) : super(RequestCache.cacheMinute, onUpdate, renew: renew) {
+    start("MarianumMobile", "message");
+  }
+
+  @override
+  GetMessagesResponse onLocalData(String json) {
+    return GetMessagesResponse.fromJson(jsonDecode(json));
+  }
+
+  @override
+  Future<GetMessagesResponse> onLoad() {
+    return GetMessages().run();
+  }
+}