[12.x] Add ability to default the mailable and notifcation queue

[jackbayliss]

The other day I was trying to find a nice way to make all my Mailables go to one queue, and Notifications to go to another.

Which, got me thinking rather than creating new base classes to extend them for all my mail / notifications classes- and then using onQueue / settings the queue property, I thought it could be nice to have this as a static property so it can be setup in the service provider and defaulted.

This also means if anyone creates a new Mailable, or Notification in my application - there's no ability to forget to extend the base class (as there isnt one!)

This means we can do something like the below and not worry about the queue as it'll default to what we set:
Mail::to($user->email)->queue(new X);
Notification::send($users, new InvoicePaid($invoice));

I don't think this is a breaking change, as it's null by default so continues on as normal if its not set.

Let me know if there's any adjustments needed / a better way 🫡

Something like this may also work for Jobs, and could sit in a config - but one step at a time.

[github-actions]

Thanks for submitting a PR!

Note that draft PR's are not reviewed. If you would like a review, please mark your pull request as ready for review in the GitHub user interface.

Pull requests that are abandoned in draft may be closed due to inactivity.