title: How to access current firebase user from iOS Today Extension?
body: <p>We're building a today widget on top of our iOS app which is working with Firebase. However we're struggling to access current signed-in user from the extension. The user at the main app is anonymous so passing credentials via shared container is not an option.</p>
  
  <p>The only way that I found is passing uid and generate custom token to sign in but I was hoping to find out better way to share FIRUser between my main app and app extension. What would be the best way to achieve this?</p>