title: MS Graph API: "Requests must contain extension changes exclusively." when trying to create calendar event
body: <p>I'm trying to create a calendar event in MS Graph API using by posting the payload below. I've tried both from Graph Explorer and my code with the same result.</p>
  
  <blockquote>
    <p>Requests must contain extension changes exclusively.</p>
  </blockquote>
  
  <p>If I try to create the event with no extension it works, and if I misspell the extension it says there's no extension with that name.</p>
  
  <p>If I look at example 3 in this link it seems I should be able to create an event with an extension using one POST.</p>
  
  <p><a href="https://docs.microsoft.com/en-us/graph/extensibility-schema-groups" rel="nofollow noreferrer">https://docs.microsoft.com/en-us/graph/extensibility-schema-groups</a></p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>{
      "organizer": {
          "emailaddress": {
              "name": "Mattias Johansson",
              "address": "my_email@mail.com"
          }
      },
      "start": {
          "dateTime": "2019-06-25T14:00:00Z",
          "timeZone": "UTC"
      },
      "end": {
          "dateTime": "2019-06-25T15:00:00Z",
          "timeZone": "UTC"
      },
      "ext46y2yz8p_activity": {
          "activityguid": "0050569A092E1ED98CEEF8728417C0D9"
      },
      "body": {
          "contenttype": "text"
      }
  }</code></pre>
  </div>
  </div>
  </p>
  
  <p>Update: 
  I tried to update an existing record with the new attribute, and that works just as expected</p>