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 migrates the previously separately managed helm chart into
this monorepo in order to profit from the already existing, unified
setup for chart and repository updates, as well as making sure, that
things keep being maintained.

It seems like the variable is not picked up properly and as a result
it doesn't work as expected.

This patch tries to use the GitLab CI feature that allows to
detect changes from a specific branch, in this case the default
branch, and this way hopefully reduces the amount of
unnecessarily build images that originate from gitlab starting
a full build by default on a new branch.

References:
https://docs.gitlab.com/15.4/ee/ci/yaml/#ruleschangescompare_to

This patch introduces an own helm chart, which is basically a
copy of the upstream chart, but with adjustments made to it, to
fit with my current style of deployment.

Given the current uncontrolled nature of adjustments to the
upstream chart, it might cause unexpected outages and alike,
moving this chart into my own repository should prevent that
and allow to use the standard flow.

Further not all my changes are upstream yet and might never be,
given that many people are working on the same problems right
now.

Refrences:
https://github.com/mastodon/mastodon/pull/20733

This patch removes the needs relation since it requires all `parallel`
jobs to be executed before continuing, which break when only one helm
chart is linted.

Error message:
'chart-package: [keycloak]' job needs 'chart-helm-unittest: [mok]' job, but 'chart-helm-unittest: [mok]' is not in any previous stage

Currently gitlab-ci doesn't allow variables in `exists` rules, which
means the condition below can't be used. This is fixed by moving the
condition into the script and just exit successful if the tests don't
exist.

Further it adds a requirement for the chart-package job to wait for the
chart-helm-unittest job(s) before, this should help to prevent the
release of broken charts.

Finally we namespace the junit files generated during the tests, since
they would overwrite each other, if multiple helm charts would run the
CI jobs at the same time.

References:
https://docs.gitlab.com/ee/ci/yaml/#needs
https://docs.gitlab.com/ee/ci/yaml/#rulesexists

This patch reorders CI steps and adjusts some names. It also adjusts the
exists rule, which doesn't seem to trigger as expected.

This patch introduces the CI integration for helm-unittest, a nice helm
plugin, which allows to run automatic tests on helm charts and
validating the YAML based on individual settings with clear reports in
gitlab.

This patch replaces the individual helm chart gitlab-ci yamls with a
common gitlab-ci yaml for all charts, that will trigger based on changes
and allow more generalised and unified CI jobs for all charts.