Publish agentk chart to charts.gitlab.io and release a stable version

The following discussion from !585 (merged) should be addressed:

• @maikelv started a discussion: (+1 comment)

  @hfyngvason I think you have to decide how we want to version this.

  My reply:

  This is good to start with. We'll revisit and publish v1.0.0 when we're confident we can provide a stable values API. Probably together with publishing to https://charts.gitlab.io

Release notes

The GitLab agent for Kubernetes is the recommended approach to connect a Kubernetes cluster with GitLab. As the name suggests, the agent has a component that needs to be installed into the user cluster. Previously, we provided a simple, Docker-based one-liner installer and a Kpt-based advanced installation method. While Kpt is a great option, we realized that many users are not familiar with it, and it is harder to automate with Terraform than Helm is.

Thanks to Eamonn McCudden contribution, the GitLab agent for Kubernetes can be installed into a user cluster from a Helm package. We have removed the Docker-based installation method with releasing the Helm package as we expect users to have helm installed on the local machines.

The Helm package exists both in the charts.gitlab.io and Artifacthub repositories.

Proposal

• Create a project gitlab-agent under https://gitlab.com/gitlab-org/charts
• Add all ~"group::configure" backend engineers as maintainers (we are all familiar enough with Helm charts to maintain it)
• Copy the contents of build/deployment/gitlab-agent-chart/ to the root of the new repository
• Coordinate with groupdistribution on getting a Pipeline trigger token for https://gitlab.com/charts/charts.gitlab.io
  • Being done in gitlab-org/charts/gitlab-agent!1 (merged)
• Add a .gitlab-ci.yml with a publish step similar to Runner's.
  • IMPORTANT: Make sure the publish job only runs on the default branch. Once the pipeline for this .gitlab-ci.yml runs with an active trigger token, the chart will get published.
  • Being done in gitlab-org/charts/gitlab-agent!1 (merged). It runs on protected tags, not branches (I set v* as protected).
• Update this project:
  • Delete build/deployment/gitlab-agent-chart/ from this repository
  • Update docs/releases.md with a note to manually bump the chart's version and appVersion