simplified code across the app and consolidated duplicated helpers

lib/api/marianumcloud/talk/room/get_room.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/foundation.dart';
-import 'package:http/http.dart' as http;
 
 import '../../nextcloud_ocs.dart';
 import '../talk_api.dart';
@@ -17,13 +16,6 @@ class GetRoom extends TalkApi<GetRoomResponse> {
   @override
   Future<GetRoomResponse> assembleAsync(String raw) =>
       compute(_parseRooms, raw);
-
-  @override
-  Future<http.Response> request(
-    Uri uri,
-    Object? body,
-    Map<String, String>? headers,
-  ) => http.get(uri, headers: headers);
 }
 
 GetRoomResponse _parseRooms(String raw) =>