title: Firebase SignIn with idToken or refreshToken
body: <p>When a user signs into my app with Firebase auth, I save both the returned idToken and refreshToken as cookies.  When the app is refreshed, rather than making the user go through the sign in process again, I'd like to just pull these stored tokens and re-auth with them.  So I would just provide a token, and the <code>currentUser</code> would be the same as it was before the refresh occurred.  As far as I can tell from the <a href="https://firebase.google.com/docs/reference/js/firebase.auth.Auth" rel="nofollow noreferrer">firebase docs</a> on the matter, there is no way to trigger a "sign in" just from these tokens.  What can I do?  Or does Firebase store its own cookies to persist the <code>currentUser</code> across refreshes?</p>