hammer-cli has a release flow, but it's broken.

It's only triggered on tags with a v prefix: https://github.com/theforeman/hammer-cli/blob/0802c796699108a189306f4f1ae327110f97552e/.github/workflows/release.yml#L7

In addition, it uses voxpupuli/ruby-release which internally uses gem build but Hammer is supposed to use rake build: https://github.com/theforeman/hammer-cli/blob/0802c796699108a189306f4f1ae327110f97552e/.github/workflows/release.yml#L20

It documents the release process in rel-eng/README.md but we should track this in RELEASE.md and update where needed.