Add image metadata to building pipeline

[adamcstephens]

It was pointed out to me that our images currently have a description of Nixos unstable arm64 (20250128_01:00). This is not the correct casing for the distribution, which should be NixOS. I'm not seeing this available for us to customize, so can you look into this @stgraber ? Thanks!

[stgraber]

I suspect the logic on the image server is as simple as capitalizing the first letter of the string

[stgraber]

Yeah, definitely looks that way as all distro and release names follow that pattern regardless of their preferred casing

[adamcstephens]

Is that something that can or should be fixed?

[stgraber]

Probably should be fixed but exact fix isn't clear yet.

I'd rather not have to hardcode the correct naming for all distros and releases in our publishing logic.
So we'd probably need something in distrobuilder to handle that and then have the publisher logic read that data while building the index.

[adamcstephens]

Wearing a distro maintainer hat, I guess it would be nice if we could customize this in the image yaml definition in this repo. Maybe with a fallback to the current name if not defined in the yaml.

[stgraber]

Yeah, there are a few things I'd like to move into some kind of publish.yaml file or something as part of the image build:

• Image description
• Needed capabilities (secureboot, agent disk, ...)