auth/gcp: add support for sovereign cloud artifact registry

[matheuscscp]

Closes: fluxcd/flux2#5874

This will unblock support only for controller-level workload identity. The Google libraries will read the environment variables internally when using controller-level workload identity. For object-level we will need new API surface, to be covered in a new RFC I'm working on.

[stefanprodan]

LGTM

[fluxcdbot]

Successfully created backport PR for flux/v2.8.x:

• [flux/v2.8.x] auth/gcp: add support for sovereign cloud artifact registry #1202

[zodd3131]

Hello Matheus,
Thank you for the work done.

I should have been more specific. Container images on s3ns are formatted this way :
docker.s3nsregistry.fr/s3ns/<project_id>/<artifact_registry_name>/<path_to_image>:

Contrary to gcp, there is no prefix with the location. "u-france-east1" doesn't show up on image name.

i think regexp should be change to:

const registryPattern = `^(((.+\.)?gcr\.io)|(.+-docker\.pkg\.dev)|(docker\.s3nsregistry\.fr))$`

I'm sorry I believe this change affect unit tests too.

Thank you in advance!

[matheuscscp]

@zodd3131 These docs disagree with you: https://documentation.s3ns.fr/artifact-registry/docs/docker/troubleshoot