[Enhancement]: Allow specifying application_name for custom jobs

[RobAtticus]

What type of enhancement is this?

API improvement, User experience

What subsystems and features will be improved?

Policy

What does the enhancement do?

When adding a new job (add_job), or altering an existing user-defined job (alter_job), it would be nice to be able to give it a custom name. When a database has more than a few custom jobs, seeing "User defined job" is not as useful to figure out which is running.

Implementation challenges

alter_job could get tricky if you want to prevent users from renaming built-in jobs. So I'd settle for add_job having the parameter.