Automate Katello gem releases

[ekohl]

For tagging we have tag_{project,push} helper scripts. 457f7f5 intended to make it work, but looks like the process is different enough because Katello submits a PR before and assumes the commit is already made where Foreman has the script make that commit.

Once we resolve that, you should be able to copy the exact same instructions as Foreman:

theforeman-rel-eng/procedures/foreman/release.md.erb

Lines 35 to 37 in de3b841

	- Tag the projects
	- [ ] Create tags using <%= rel_eng_script('tag_project') %>
	- [ ] Push tags using <%= rel_eng_script('tag_push') %>

Then the steps to generate the .mo files and call gem build etc would be equivalent to Foreman's release_tarballs step (since the tarballs are the release artifacts for Foreman). That should be kept in for now.

We can also automate gem releases. We already have that for other plugins after a tag is pushed. See https://community.theforeman.org/t/use-trusted-publishers-to-release-gems/42009 for how we've done that. Only exception is that the .mo file building isn't part of it, but we can move that to RPM packaging instead.

Having said all of that: it would rely on updating the settings to match. Right now the version isn't updated since RC1:

theforeman-rel-eng/releases/katello/4.16/settings

Line 1 in de3b841

FULLVERSION='4.16.0-rc1'

I'd prefer to capture this in an issue upstream and if you want you can point a JIRA issue at it. Thoughts?

Originally posted by @ekohl in #472 (comment)