Abstract database backup storage secrets

[j-zimnowoda]

Is your feature request related to a problem? Please describe.

In the values/harbor/harbor-raw.gotmpl there is a block of secrets that are needed for database backup process. The same secrets will be defined for other apps in different namespaces.

Describe the solution you'd like A clear and concise description of what you want to happen. We would like to abstract this part as a reusable template file.