title: Register a user within asp.net identify
body: <p>The authentification process of my app is based on the azure mobile app authentification (facebook).
  But in the background I have to register a user account. </p>
  
  <p><strong>So where is the right spot to register a user inside of azure mobile app application?</strong>
  And where can I set some custom claims like <code>Role</code>?</p>
  
  <p>Do I have to create a custom AppServiceTokenHandler?
  Or are there any better spots?</p>