Update release process

[rudigiesler]

Purpose

The current release procedure is complex and difficult to understand. It also doesn't match our current development speed, and users often want features much earlier than releases.

Approach

This PR puts together a proposal for a simpler release process, that hopefully better matches the development and usage of contentrepo

It also adds documentation on how to actually create a release.

[jerith]

Do we want a new dev release for each feature that goes to QA?

It might make sense once the pace of development slows down somewhat, but at the moment I expect it'll be more of a barrier than a help.

[rudigiesler]

Yeah I guess we don't need it, we can rely on just the SHA hashes. Should we get rid of dev releases completely then?

[jerith]

Dev releases may still be useful, especially if we have some experimental features that we want to deploy somewhere less volatile than a shared QA environment. I think we can leave them in, but remove the item about using them for QA deployments.

Somewhat unrelated: Do we want a version check in version-tagged image builds to make sure the pyproject.toml version matches the tag?

[rudigiesler]

Yeah we can add that, good idea. You can move a tag to a different commit right?

[fritzbrand]

Thanks, looks good to me