This patch adds `automountServiceAccountToken: false` to various
ServiceAccount objects in order to disable automatic mounting of service
accounts tokens to Pods that never need to use them.

Skipping 22.0.2 as recommended by release notes.

References:
https://www.keycloak.org/2023/09/keycloak-2203-released.html

This patch adjusts the keycloak helm chart to use the upstream
recommended paths for exposing keycloak. It also adjusts the current
deployment to utilise a dedicated, further restricted admin interface.

BREAKING CHANGE: This commit will remove the exposure of the admin
interface as well as other exposed URLs.

References:
https://www.keycloak.org/server/reverseproxy#_exposed_path_recommendations

The helm-unittest upstream has switched back to the helm-unittest
organisation again. Therefore switching to a different image. With the
switch a few minor, but breaking changes have been introduced.

- Dropping helm v2 support
- adjustment of indentation
- enforcing jsonpath for selection

Reference:
https://github.com/helm-unittest/helm-unittest

This patch upgrades keycloak to 20.0.0 and implements the new
adminHostname feature by adding the required variables and a separate
ingress object, which can be utilised for the admin URL and restrict it
independent of the regular frontend.