async function update(req, res) {
    const calendar = await gladys.calendar.update(req.params.calendar_selector, req.body);
    res.json(calendar);
  }
@api {patch} /api/v1/calendar/:calendar_selector update
@apiName update
@apiGroup Calendar
@apiUse CalendarParam
@apiSuccessExample {json} Success-Example
{
  "id": "b3eeebd8-58f2-4694-83a6-0b2cca871a5d",
  "name": "My calendar",
  "selector": "my-calendar"
  "description": "My personal events",
  "sync": true,
  "notify": false,
  "user_id": "e4e3f03e-60b9-485e-bc0a-c582b69089bd",
  "updated_at": "2019-05-09T03:14:29.820Z",
  "created_at": "2019-05-09T03:14:29.820Z"
}