[5.5] Enhance Mailable queueing

[aleksandrlat]

It is impossible to enhance or change queue job in Mailable now.

For example it would be nice to add failed method to Job to handle job failures. But it is impossible now.

With job factory method we can use any custom Job for Mailables. It will be possible to add failed method.

[taylorotwell]

I would rather just support failed in Mailables and Notifications, etc.

@themsaid is it not possible already?

[aleksandrlat]

failed is one of use cases. There maybe other probably.
Having failed in Mailables and Notifications would be nice.

[taylorotwell]

I would rather do that than hack this in. @themsaid

[themsaid]

@taylorotwell Here's a PR to support failed() in mailable and notifictaions: #21585

@aleksandrlat what else do you think should be supported?

[aleksandrlat]

I just thought about other potential tasks. I don't have something concrete in mind.

@themsaid thank you for failed method.