add custom labels to database - database environment

[y16144]

this can ensure better visibility or evaluation over the existing environments - e.g. monitoring - Prometheus/grafana - elasticsearch ...

[eberlep]

We already use custom labels on the pods, and we already have custom labels via cloudctl (which are not passed along to the pods). We could simply combine the two, but that would (unexpectedly) cause the pods to roll if you were changing those labels via cloudctl.

It is probably better to introduce a new PodLabels list in our custom resource and pass those values along. Changing those would still trigger the pods to roll, but at least that should be more obvious (it already contains pod in the name, after all).