title: Does firebase auth store and manage access token for different provider
body: <p>I am working on a flutter app where the user will sign-in using Facebook. Later I want to access facebook graph API and for then I need the access token of the user.</p>
  
  <p>I of now I am storing the access token in firestore and assessing from there. But is there any way using which we can get the access token from currentUser. Because in the current situation the access then gets expired and I need to refresh it again and again. Does firebase handle it automatically?</p>
  
  <p>Below is my code which I use to sign in with Facebook using firebase.</p>
  
  <pre><code>FacebookLogin facebookLogin = new FacebookLogin();
  FacebookLoginResult result = await facebookLogin.logIn(['email', 'public_profile', 'user_friends']);
  switch (result.status) {
      case FacebookLoginStatus.loggedIn:
          AuthCredential authCredential = FacebookAuthProvider.getCredential(accessToken: result.accessToken.token);
              FirebaseUser user = (await FirebaseAuth.instance.signInWithCredential(authCredential)).user;
          //Here I save user details in firestore
  }
  </code></pre>