title: Firebase FCM force onTokenRefresh() to be called
body: <p>I am migrating my app from GCM to FCM.</p>
  
  <p>When a new user installs my app, the <code>onTokenRefresh()</code> is automatically being called. The problem is that the user is not logged in yet (No user id).</p>
  
  <p>How can I trigger the <code>onTokenRefresh()</code> after the user is logged-in?</p>