Add Rails standard ApplicationJob for consistency

[mkllnk]

What? Why?

New Rails apps come with this class already, the job generator creates it for every new job and Rubocop requires it as well. Let's make our lives easier and use the same structure as other Rails projects. This class may be handy one day.

This came up in:

• Add webhook triggered on Order Cycle Open #9687 (comment)
• Render reports in a separate process (feature-toggled) #10258 (comment)

What should we test?

• Specs pass.

Release notes

Changelog Category: Technical changes

The title of the pull request will be included in the release notes.

Dependencies

Documentation updates

[dacook]

I approve
It's semantically exactly the same as before so I can't imagine the specs would fail, but will wait to make sure before marking ready to go.

[dacook]

Spec flakiness :(

 Ferrum::ProcessTimeoutError:
   Browser did not produce websocket url within 20 seconds, try to increase `:process_timeout`.