title: API call to calendar.events.insert failed with error: Invalid conference type value
body: <p>I am trying to build third party conferencing google calendar add-on.
  For creating conference data, I am passing below object.</p>
  
  <pre><code>"conferenceData": {
          "createRequest": {
            "requestId": '7qxalsvy0e',
            "conferenceSolutionKey": {
              "type": 'addOn'
            }
          }
  };
  </code></pre>
  
  <p>GoogleJsonResponseException: API call to calendar.events.insert failed with error: Invalid conference type value.</p>
  
  <p>Is something missing or wrong value is passed?</p>