* Fix check for existing jobs
If a job is to be enqueued once and no specific scheduled time is
specified, any scheduled time of existing jobs will be valid. Only if a
specific scheduled time is specified for 'enqueue_once()' can it be
evaluated.
* Allow system jobs to be registered
A new registry key allows background system jobs to be registered and
automatically scheduled when rqworker starts.
* Test scheduling of system jobs
* Fix plugins scheduled job documentation
The documentation reflected a non-production state of the JobRunner
framework left over from development. Now a more practical example
demonstrates the usage.
* Allow plugins to register system jobs
* Rename system job metadata
To clarify which meta-attributes belong to system jobs, each of them is
now prefixed with 'system_'.
* Add predefined job interval choices
* Remove 'system_enabled' JobRunner attribute
Previously, the 'system_enabled' attribute was used to control whether a
job should run or not. However, this can also be accomplished by
evaluating the job's interval.
* Fix test
* Use a decorator to register system jobs
* Specify interval when registering system job
* Update documentation
---------
Co-authored-by: Jeremy Stretch <jstretch@netboxlabs.com>
* Initial work on #13381
* Fix backend type display in table column
* Fix data source type choices during bulk edit
* Misc cleanup
* Move backend utils from core app to netbox
* Move backend type validation from serializer to model