title: How to store Firebase Auth users' credentials on device to quickly switch accounts later?
body: <p>I want to implement the UX where it is possible to quickly switch between previously signed in Firebase Auth users e.g. from a navigation drawer like Google apps do:</p>
  
  <p><a href="https://i.stack.imgur.com/FHjrY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FHjrY.png" alt="Account switcher"></a></p>
  
  <p>The problem is that Firebase docs and samples only implement the "sign in - sign out" flow, where switching users would require signing out first and then reentering a password / repeating auth flow with Facebook etc., instead of just switching with a single tap. Google advocates for Smart Lock, but it's only good for email and Google auth providers, and is generally not the UX I'm seeking.</p>
  
  <p>What is the proper way to store those users and their credentials? The solution must support users authenticated via any of the supported providers, such as email/password, Google, Facebook, etc.</p>
  
  <p>Since authenticating with either method results in obtaining an <code>AuthCredential</code> object, perhaps the question boils down to how to securely store those objects on the device, and whether they can be reused later.</p>