Add Cron trait for Tasks.

[technosophos]

This may be a tricky one because Kubernetes distinguishes between Job and CronJob.... so it sorta changes the workload type

[hongchaodeng]

How about make a "CronTask" workload?
That would be closer to k8s.

[technosophos]

Feel free to propose that in the spec repo. The earlier feeling had been that running periodically is an operational aspect, not a developer decision. I tend to agree with that, though I don't know how to make that work with the way Kubernetes does CronJob objects. Essentially, we would have to write a trait that replaces the Job with a CronJob, and that seems beyond the scope of what a trait ought to do.

[technosophos]

I think we should consider this one "low priority" since it is both difficult and not defined in the core spec.