Operation mode with batch job support but without a job registry or job tracker

[soxofaan]

A functional deployment with full batch job support currently requires a job registry (e.g. EJR) and a regular (e.g. minutely) run of the job tracker.

These extra components can make it quite challenging to get a working deployment (e.g. in EOEPCA https://github.com/EOEPCA/roadmap/issues/332).

I wonder if it isn't feasible to have operation mode that does not require a job registry (nor a job tracker to keep that job registry up to date): just query the cluster API directly to get the state of a job.

This mode would probably not be recommended for production use cases, but having it available could lower the bar considerably to get a working deployment for testing purposes.

It could also provide a fallback code path when the EJR code path is broken for some reason (EJR down, job tracker not running)