addAuthStateChangedCallback method
Add a callback that will be invoked when the service's authentication state changes.
The returned function will remove the callback when called.
Implementation
@override
UnsubscribeDelegate addAuthStateChangedCallback(
AuthStateChangedCallback callback) {
_authChangedCallbacks.add(callback);
return () {
_authChangedCallbacks.removeWhere((element) => element == callback);
};
}