public void LoginAnonymous(Action<bool, string> _callback)
    {
        auth.SignInAnonymouslyAsync().ContinueWithOnMainThread(_task =>
        {
            if (_task.IsCanceled)
            {
                _callback(false, "SignIn was canceled.");
                return;
            }

            if (_task.IsFaulted)
            {
                _callback?.Invoke(false, "SignIn encountered an error: " + _task.Exception);
                return;
            }

            firebaseUser = _task.Result.User;
            _callback?.Invoke(true, string.Empty);
        });
    }