Use Notification/Notifiable (#379)

* Add migrations for notifiables

* Configure spatie-backup to run as part of cron

* Convert Mailer to Notification; add pirep notifications

* Styling

resources/views/mail/user/rejected.blade.php

@@ -0,0 +1,9 @@
+@component('mail::message')
+# Hi {{ $user->name }},
+
+Your registration to our airline was denied. Please contact
+an administrator with any questions you may have.
+
+Thanks,<br>
+Management, {{ config('app.name') }}
+@endcomponent