Support for env variables from secret for logical backup

[stgrace]

Please, answer some short questions which should help us to understand your problem / question better?

• Which image of the operator are you using? e.g. registry.opensource.zalan.do/acid/postgres-operator:v1.8.2
• Are you running Postgres Operator in production? yes
• Type of issue? feature request

I would like to see an option to add environment variables from a secret for logical backup cronjobs. This would allow postgres config to not contain secrets and for secrets to be created from another source (sealed secrets/manual creation/external operator/...).