use Kubernetes CronJob instead of sidekar with cronjob daemon

[rriemann]

Description of the change

Assume in the values.yaml the cronjob is enabled:

cronjob:
  enabled: true

This requires a permanently running container as it is implemented as a container in the nextcloud deployment. One could use a K8s cronjob instead.

https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/

Benefits

If a K8s cronjob would be used instead, the resources would be freed when the cronjob is not running. At least this is my understanding.

Possible drawbacks

If the frequency is very high, the time of launching the container and stopping may not allow many other jobs to run in between.

[provokateurin]

It was like that in the past and there were problems, that's why it was changed to be a permanent container instead. I think there recently was another issue with a similar request and you should also be able to find the old issues/PRs from when this was changed.
PRs are always welcome and we try to review them in a timely manner.