Add the option to store the config as ConfigMap

[mheuser]

Preflight Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Problem Description

I want to be able to use a ConfigMap instead of a Secret for storing the config. Dex makes it possible to not need actual secrets in the config. We can use env vars for that as seen in the Dex GitHub example.

This makes it easier (at least for me) to integrate this chart into e.g. external-secrets, jenkins x, hashicorp vault and similar.

Proposed Solution

Add an field configType with secret set as default - so no breaking change - and configMap as option. Handling of the ConfigMap analogue to the Secret handling.

Alternatives Considered

Subcharting this Chart. Since there is no option to not reference the secret in the volumes section of the deployment this is not possible.

Additional Information

No response