Note, I'm unsure if the version-differential schema should be generated, it's handwritten for now.

@mikem what do you think about adding another archivetype? I'm 60% plus here as we've already those other raw variants.

As some additional information, it won't exactly be common to use zstd since the time/space tradeoff for it favors local builds more than build systems.

However, there are (one) Fedora spins that would like to also provide this archive format aside from xz. The reasoning is that it seems to perform much better for unpacking on resource constrained devices.

Yes, the question is if it should be part of basic installation. It is easy to add it via API to running instance (koji call addArchiveType raw-zst 'zst compressed raw disk image' 'raw.zst') Sadly, we're historically not consistent what is part of initial data and what should be defined per running instance.