Allow the PostgreSQL collector to derive the PostgreSQL password from a kubernetes secret

[Mahoney]

Describe the rationale for the suggested feature.

Currently you can only pass a password to the PostgreSQL Collector as a plain text string in the URL (e.g. uri: postgresql://user:password@hostname:5432/defaultdb?sslmode=require).

Typically this is not secure, and if you are using a helm chart for your app you are probably creating a kubernetes secret to contain the password, whether to an external database or to one you are creating inside the cluster.

I don't know if this SupportBundle check runs inside or outside the cluster, but assuming it runs inside it would be good to be able to use that secret to provide the password for this collector.