Use secrets instead of hardcoding credentials in the values.yaml file about helm-charts

[oliverguenther]

I suppose this can be closed with the changes in #46, / version 4.0.0.

[johanneskastl]

I can confirm that it works! At least for the postgreSQL database.

I do not use the bundled one, so I need the following settings:

postgresql:
  bundled: false
  connection:
    host: <service-name-here>
    port: 5432
  auth:
    existingSecret: my-postgresql-credentials-secret
    secretKeys:
      userPasswordKey: "password"

As soon as I set the auth.existingSecret, I need to add the secretKeys. But that is to be expected, as it is commented out in the chart's values.yaml and hence there is no default value for this.

Thanks for the work @oliverguenther @machisuji