Enhance management of Job Schedulers

[lpoulin]

Is your feature request related to a problem? Please describe.
It is a little frustrating that you cannot get all of the data back on a job scheduler that it was created with. I would like to display job schedulers in our application so they can be modified, but there doesn't appear to be a way to view the job template, so I can't populate the form with the existing values before upserting.

Describe the solution you'd like
It would be nice if JobScheduler could be its own type instead of trying to squeeze it into RepeatableJob, since the class lacks all of the properties that a job scheduler has, like the job template. Perhaps the API could also support getting jobs that were produced by a job scheduler, or at least have some indication on the Job itself that it was produced by a job scheduler.

Additionally, I would like to be able query for a single job scheduler, instead of fetching all of them from a queue and then filtering on the ID.

Additional context

{"key":"ExampleJobScheduler","name":"ExampleJobScheduler","endDate":null,"tz":null,"pattern":"*/30 * * * * *","every":null,"next":1730314440000}

Above is all of the information you get back when retrieving a job scheduler. How am I supposed to know what the job template looks like so I can determine if I need to make changes to it?