Integrate K8up Helm chart into this repository

[ccremer]

Summary

As developer
I want to maintain the K8up Helm chart in this repository
So that I don't have to maintain the deployment config with Kustomize and in an external Helm repo.

As K8up Admin
I want to install a K8up Helm chart version that redistributes the K8up CRDs
So that I don't have to select the K8up version that is included in the Chart separately

Context

This is about migrating the K8up Helm chart into this repository.

We should make a new major release to clearly communicate the switch to another repository.

These are basically the things to do:

• Integrate the existing K8up Chart into this repository
• Copy the GitHub automation from https://github.com/vshn/appcat-service-postgresql
• Add labels as required in https://vshn.github.io/appcat-service-postgresql/appcat-service-postgresql/how-tos/create-releases.html
• Release the chart as v3.0.0 with "upgrade" documentation
• Deprecate the chart in appuio org (https://github.com/appuio/charts/tree/master/appuio/k8up) with redirection notice to this repo.
• Get rid of the Kustomize setup, or more precise: Make it so that generated artifacts are able to be integrated into the chart (see https://github.com/vshn/appcat-service-postgresql/blob/8b9c15adeb1097c568eb172bec44c9e1b5f9a6ca/charts/provider-postgresql/Makefile as example)
• Ensure the e2e tests work with the Helm chart after getting rid of Kustomize method.
• Update installation docs in https://k8up.io/k8up/how-tos/installation.html (Remove the installation steps there and link to the chart README, Remove Kustomize option)

Out of Scope

• Migrating existing Helm chart releases

Further links

• Reason why we don't ship CRDs in the Helm chart
• Idea to include K8up CRDs into GitHub release of Helm chart: [k8up] Attach CRDs to GitHub release appuio/charts#419
• K8up Helm chart

Acceptance Criteria

• Given master branch in the K8up repository, when I browse the contents then there is a fully-documented Helm chart available that installs K8up operator (without CRDs) and the Kustomize setup is deleted.
• Given master branch of the K8up repository, when I run make e2e-test then the operator is installed with the local chart instead of Kustomize.
• Given master branch of the K8up repository, when I run make generate then the RBAC roles and rules are generated in the Helm templates directory and enriched with Helm labeling functions.
• Given K8up repository, when I want to make breaking changes to the chart, then I don't need to bump K8up (operator) major version
• Given K8up documentation, when I want to release K8up, then I can look up a documented release process.
• Given I want to make changes to the Helm chart, when I create a PR, then a PR job ensures that the chart is following quality standards (for example documentation with helm-docs).
• Release documentation is updated here: https://k8up.io/k8up/2.2/explanations/release.html

Implementation Ideas

• when I push a vX.Y.Z Git tag, then K8up (operator) is released with changelog excluding changes to the K8up chart.
• when I push a chart-X.Y.Z Git tag, then K8up chart is released with changelog containing only changes to the K8up chart and the release contains the CRDs corresponding to the K8up version.

[ccremer]

Note: In vshn/appcat-service-postgresql#39 (and some commits afterwards) we have already engineered the automation for this type of repo and releasing. I also ironed out some issues that came up with such a design.
I'm going to reword the acceptance criteria to match it.

[ccremer]

this is actually done