feat: Add autogroup ACLs

[gabe565]

I have taken @vinhjaxt's autogroup implementation from #657 (comment), added some code improvements, fixed lint, and added tests. This is still a WIP, but so far it's working as intended.

• have read the CONTRIBUTING.md file
• raised a GitHub issue or discussed it on the projects chat beforehand
• added unit tests
• added integration tests
• updated documentation if needed
• updated CHANGELOG.md

Fixes #657

[kradalby]

Im on holiday so wont have time to take a look for a few weeks but wanted to just jump in and say that I have started work to redo the policy code, there is a draft pr, but its very draft pending many changes.

I don't imagine I would add anything new to the policy as is, so this should be added on top of the new work. That said it might not be in the final state and it might be hard to do so yet.

I do appreciate you picking this up, and would love to see it in when we get there.

[AdamsGH]

Really waiting for this feature!

[danscarfe]

Hey, any update here. Really looking forward to this function and kind of blocked without it (without changing from using main image)

[vdovhanych]

I have reimplemented this in policy v2 and will test it more in my home lab environment to see if it's working as expected. It's pretty much the same logic as the code here, but it is done in the way policy v2 is written.

[kradalby]

Sounds sensible, main criteria is tests, happy also to help with it as we want to get there eventually, but might say thst we want to wait one release with this one

[kradalby]

https://github.com/juanfont/headscale/releases/tag/v0.26.0-beta.1, new beta is out, I think it should be fairly safe to rebase this onto that branch and if we get it proper tested it should be something we can get into 0.27.

Targeting 0.27, no v1 code needs to be considered.

[kradalby]

I'm going to close this in favour of @vdovhanych's PR, and some collaborations on getting this in as this PR is out of date.