code: function postAddZSetMember (req, res, next) {
      let key = req.body.key;
      let score = req.body.score;
      let value = req.body.value;
      let connectionId = req.body.connectionId;
      getConnection(req, res, function () {
          addZSetMember(key, score, value, res, next);
      }, connectionId);
  }
docs: sorted set