Due to an influx of spam, we have had to temporarily disable account registrations. Please write an email to accountsupport@archlinux.org, with your desired username, if you want to get access. Sorry for the inconvenience.
https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry#labelling-container-images and https://github.com/opencontainers/image-spec/blob/main/annotations.md#pre-defined-annotation-keys