Cron job and unique jobs composability

[vemv]

Hi!

Thank you for this library.

https://github.com/keypup-io/cloudtasker/blob/master/docs/UNIQUE_JOBS.md and https://github.com/keypup-io/cloudtasker/blob/master/docs/CRON_JOBS.md are great documents individually.

However it is not hinted how "cron" and "unique" jobs may compose (or if that is a supported use case at all).

Consider this use case:

• I want to run a cron job every 5 minutes
• But, due to arbitrary circumstances (slow APIs, bugs, etc), the job implementation may take more than 5 minutes to execute
• Then, it's not necessarily clear what will happen to subsequently scheduled jobs. The cron schedule may result an in a temporal overlap.
  • Will they be concurrently scheduled/executed?
  • If the jobs were defined as unique, will the cloudtasker_options lock: options possibly cause a strategy such as reject or reschedule to be triggered?

From my side, I'd be happy with any behavior that was guaranteed, simple and sequential (no concurrency).

Thanks - V