public function postToken(Request $request)
    {
        $this->validate($request, ['token' => 'required']);

        if (! session('spark:auth:id')) {
            return redirect('login');
        }

        $model = config('auth.model');

        $user = (new $model)->findOrFail(
            $request->session()->pull('spark:auth:id')
        );

        if (Spark::twoFactorProvider()->tokenIsValid($user, $request->token)) {
            Auth::login($user);

            return redirect()->intended($this->redirectPath());
        } else {
            return back();
        }
    }