Ability to use a secret for the password for authentication

[jack1902]

Currently, in order to enable authentication on cmak with this chart, you can do the following:

ui:
  # enable basic auth on the UI
  extraArgs:
    - "-DbasicAuthentication.enabled=true"
    - "-DbasicAuthentication.username=<username>"
    - "-DbasicAuthentication.password=<password>"

This results in the password being stored on the manifest within the cluster, which enables anyone with read access to get the manifest AND the password for cmak. It would be ideal if something similar to the below could be allowed such that the chart was extended in capabilities like so:

---
# Values file
authentication:
  enabled: false
  username: ""
  password: ""

I'll open a PR to show this as I really want to avoid exposing a secret via a manifest