title: MUC/Sub Remove user subscription automatically
body: <p>I am trying to develop a chat app using Ejabberd 16.09, the only way i find to unsubscribe a user is</p>
  
  <pre><code>&lt;iq from='hag66@shakespeare.example'
  to='coven@muc.shakespeare.example'
  type='set'
  id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'&gt;
  </code></pre>
  
  <p>
  
  There is any way to automatically unsubscribe the user when he leave the room?</p>
  
  <p>Or anyway to someone else to remove his subscription?</p>