code: private void addAttributes(PublisherRegistration publisherRegistration, String group) {
          // if group == null; group = "DEFAULT_GROUP"
          if (StringUtils.isNotEmpty(group)) {
              publisherRegistration.setGroup(group);
          }
  
      }
docs: 添加额外的属性
  
  @param publisherRegistration 注册或者订阅对象
  @param group           分组