Handle Failed Subscriptions On Laravel-Spark

I'm using Laravel-spark version 4.0.0 , I want to handle failed subscriptions on laravel- spark ,This is a feature provided by laravel - Cashier package as mentioned in the documentation :

Failed Subscriptions :
What if a customer's credit card expires? No worries - Cashier includes a Webhook controller that can easily cancel the customer's subscription for you. As noted above, all you need to do is point a route to the controller:

Route::post(
    'stripe/webhook',
    '\Laravel\Cashier\Http\Controllers\WebhookController@handleWebhook'
);

http://ift.tt/2xzI18M
Now I want to handle this case on laravel spark , It seems that they didn't handle failed subscription on this version. any suggestions to start ?

via Chebli Mohamed