Convert the Laravel Spark invoice email to a Mail Notification email

Recently when customizing the invoice email template for Laravel Spark I noticed that it didn’t have any styles applied (raw HTML emails are a bit 1999). Given how good the new Mail Notifications look in Laravel 5.3 I figured it would make sense to convert the existing invoice email template to the new Mail Notifications. Here is how I did it:

Note that I had to create a new custom.php route file so that the web middleware wasn’t being applied to the Stripe webhook route, hence the modification to RouteServiceProvider.