Look into storing users separately in keycloak backup

Currently keycloak configuration and users are backed up in the same file. I think it would be better to back them up separately. We want to be able to share configurations without sharing users. Or roll back either independently.

There is a function for that, but we are not yet sure how to recover the users after a backup. Would be worth looking into and changing the script accordingly.

_Original discussion https://github.com/aiondemand/AIOD-rest-api/pull/286#discussion_r1575848093_