title: Remove FCM token from Firebase device group
body: <p>I'm using Firebase Device group to notify all device of a user. 
  <a href="https://firebase.google.com/docs/cloud-messaging/android/device-group" rel="noreferrer">https://firebase.google.com/docs/cloud-messaging/android/device-group</a></p>
  
  <p>In order to stop notifications on a device I call:</p>
  
  <pre><code>FirebaseInstanceId.getInstance().deleteInstanceId();
  </code></pre>
  
  <p>(see <a href="https://developers.google.com/android/reference/com/google/android/gms/iid/InstanceID" rel="noreferrer">https://developers.google.com/android/reference/com/google/android/gms/iid/InstanceID</a>)</p>
  
  <p>The token is well deleted/invalidated for unique device message, if I notify this device with the firebase console we got an error message. 
  However, the token is not deleted/invalidated from the firebase device group. If we notify the user's firebase device group this device is still notified. </p>
  
  <p>I also tried to remove the token with the HTTP request (first link) on the device group, and it works. But, if the user logout offline and delete app data, I have no way to retrieve the previous user FCM group token to invalidate the current FCM token.</p>
  
  <p>Do you have some advices?
  Thank you.</p>