code: public static MessageDto joinGroup(JoinGroupParams joinGroupParams) {
          MessageDto msg = new MessageDto();
          msg.setGroupId(joinGroupParams.getGroupId());
          msg.setAction(MessageConstants.ACTION_JOIN_GROUP);
          msg.setData(joinGroupParams);
          return msg;
      }
docs: 加入事务组
  
  @param joinGroupParams joinGroupParams
  @return MessageDto