docs: public void flagStream(Stream stream, final KickflipCallback cb) {
          if (!assertActiveUserAvailable(cb)) return;
          GenericData data = new GenericData();
          data.put("uuid", getActiveUser().getUUID());
          data.put("stream_id", stream.getStreamId());
  
          post(FLAG_STREAM, new UrlEncodedContent(data), Stream.class, cb);
      }