Allow overriding of secret keys for database

[gmemstr]

I currently use the the CrunchyData Postgres Operator in my cluster, which provisions secrets for PostgreSQL users with the username and password. These contain keys that cannot be modified (from what I can tell), so this change allows the value to be overridden.

Before:

secret: postgres-connection-details

After:

secret:
  name: postgres-connection-details
  username: user
  password: pass

[samip5]

Change log annotation is missing from Chart.yaml at least.

[samip5]

Also this should be a major bump, due to incompatible backwards compatibility if one uses that secret definition like I actually do.

[gmemstr]

Good point, will update!

[samip5]

Lint failure in values.yaml: Error: 102:14 [trailing-spaces] trailing spaces

[samip5]

@gmemstr Are you aware of these errors?

Error: template: piped/templates/backend/configmap.yaml:68:64: executing "piped/templates/backend/configmap.yaml" at <.Values.backend.config.database.secret.name>: can't evaluate field name in type interface {}

When secret is defined, but the optional things are not?