title: MS GRAPH REST API - add event error when adding attendees
body: <p>I am trying to create an event into the shared calendar (meeting room) and I get an error when trying to put myself as an attendee. However the event is created into the meeting room's calendar but not into my own (the attendee's calendar).</p>
  
  <p>Preconditions:
  User A = logged user (user_A@company.com)
  User B = target meeting room (user_B@company.com)</p>
  
  <p>User A has permissions to write into User's B calendar.</p>
  
  <p>This is the call request url:</p>
  
  <pre><code>https://graph.microsoft.com/v1.0/users/user_B@company.com/events
  </code></pre>
  
  <p>Request body:</p>
  
  <pre><code>{
    "iCalUId": "user_B@company.com",
    "reminderMinutesBeforeStart": 15,
    "isReminderOn": true,
    "subject": "test",
    "start" : {
        "dateTime": "2017-02-22T10:00:00",
        "timeZone": "Europe/Prague"
    },
    "end" : {
        "dateTime": "2017-02-22T11:00:00",
        "timeZone": "Europe/Prague"
    },
    "attendees":[
        {
            "emailAddress": { "address": "user_A@company.com" },
            "type": "required",
            "status" : { "response": "accepted" }      
        }
    ]
  }
  </code></pre>
  
  <p>The response:</p>
  
  <pre><code>client-request-id: 12542206-5490-4d21-b5e8-e9a32b1d3fc1
  content-type: application/json
  cache-control: private
  request-id: 12542206-5490-4d21-b5e8-e9a32b1d3fc1
  Status Code: 500
  {
      "error": {
          "code": "ErrorInternalServerError",
          "message": "Value cannot be null.\r\nParameter name: Argument#1 (id) shouldn't be null.",
          "innerError": {
              "request-id": "12542206-5490-4d21-b5e8-e9a32b1d3fc1",
              "date": "2017-02-22T08:20:53"
          }
      }
  }
  </code></pre>
  
  <p>The error is not really informative for me because there is no ID parameter described in the API for the call. 
  And I also think there should be an email sent to User A once the event is created and the user is added as an attendee. I do not get the email.
  May it be caused by some AD misconfiguration? Or what do I miss here, please?</p>
  
  <p>P.S., 
  If I add the event into my own calendar and add the meeting room as an attendee, it works fine, email is sent and event accepted. There is a delay tho, the event appears in the meeting room's calendar approx 20 seconds later which is the reason I need to do it vice versa as described in the question!</p>