Enqueue jobs with a specified Id

I would like to when creating a background job via BackgroundJob class, to have the ability to define my own job id just like we do with re-occurring jobs.

My use case is that i have a task to performed at a random interval and as such need to use a background job with the job invocation triggering the next background job. The benefit of being able to specify the job id is that i can easily cancel the next scheduled run, if the configuration in my portal is changed.

Start by reading the BackgroundJob class and comparing its enqueue behavior with the existing recurring-job API, which already supports a specified job ID. Clarify the API and lifecycle requirements for caller-defined IDs, including how a follow-up scheduled job would be cancelled when configuration changes.

Written by the indexing model from the issue text.