accept = (req, res) => {
    this._model.update({
        user: new mongoose.Types.ObjectId(req.params.uid)
    }, {
        $set: {
            status: 'active'
        },
    }, (err, obj) => {
        if (err || !obj) {
          res.send(err);
        } else {
           res.send(obj);

        }
    });
}

{
   "_id":"5d3189a00789e24a23438a0d",
   "status":"active",
   "code":"CT-123-345-234-233-423344",
   "created_Date":"2019-07-19T09:13:04.297Z",
   "updated_Date":"2019-07-19T09:13:04.297Z",
   "__v":0
  }

api.abc.com/api/accept/5cfe4dd898fd225ef1cabdsd