Added Chat context menu for chat 'mark as read', 'mark as unread', 'add to favorites', 'remove from favorites', 'leave conversation'

added Chat favorite badge and mark chat as read when entering it

lib/api/marianumcloud/talk/leaveRoom/leaveRoom.dart

@@ -0,0 +1,19 @@
+
+import 'package:http/http.dart' as http;
+import 'package:http/http.dart';
+
+import '../talkApi.dart';
+class LeaveRoom extends TalkApi<void> {
+  String chatToken;
+
+  LeaveRoom(this.chatToken) : super("v4/room/$chatToken/participants/self", null);
+
+  @override
+  assemble(String raw) {
+  }
+
+  @override
+  Future<Response> request(Uri uri, Object? body, Map<String, String>? headers) {
+    return http.delete(uri, headers: headers);
+  }
+}