title: Use Facebook login credentials to sign in/up to my application
body: <p>I'm using Facebooks' API to get user credentials to login/sign-up to my application.</p>
  <p>But I'm struggling with what type of credentials should I save to the database as username(email) and password? should I save Facebook's user-id and token as username and password? or is there another way to do that?</p>