sign_in_form.dart

return Scaffold(
  body: SignInForm(
    authentication: Authentication.OAuth,
    stateFeedbackBuilder: (state, ..) {
      if (state is SigningIn) return const CircularProgressIndicator();
      if (state is AuthFailed) return ErrorText(state.exception);
      return null;
    },
    providers: [
      const ProviderButton<Google>();
    ],
  ),
);