docs: public MpNews getMpNews(String mediaId) {
          String url = WxEndpoint.get("url.material.mpnews.get");
  
          String json = String.format("{\"media_id\":\"%s\"}", mediaId);
          logger.info("get mpnews: {}", json);
          String response = wxClient.post(url, json);
          return JsonMapper.defaultMapper().fromJson(response, MpNews.class);
      }