Support dhi.io for az acr cache

[oscarwest]

What is the problem you're trying to solve
Add support for Docker Hardened Images upstream source in az acr cache https://docs.docker.com/dhi/

Describe the solution you'd like
Support upstream source this with az acr cache.
https://learn.microsoft.com/en-us/azure/container-registry/artifact-cache-overview#upstream-support

Additional context

az acr credential-set create \
   --registry myacr \
   --name dhi-io-creds \
   --login-server dhi.io \
   --username "..." \
   --password "..."
(UpstreamNotSupported) Unsupported upstream or login server 'dhi.io' provided. Supported upstreams or login servers are: docker.io, mcr.microsoft.com, quay.io, public.ecr.aws, ghcr.io, nvcr.io, registry.k8s.io, gcr.io, eu.gcr.io, *.pkg.dev.
Code: UpstreamNotSupported
Message: Unsupported upstream or login server 'dhi.io' provided. Supported upstreams or login servers are: docker.io, mcr.microsoft.com, quay.io, public.ecr.aws, ghcr.io, nvcr.io, registry.k8s.io, gcr.io, eu.gcr.io, *.pkg.dev.

[terencet-dev]

Thanks for your feedback request. Assigning to @toddysm

[toddysm]

Thank you @oscarwest for requesting that. We are working on capability to add any registry as upstream (see linked parent) and this should be part of that feature.

[thorfi]

+1

[toddysm]

DHI may come as additional selection in Q12026. It will be separate from the work on any registry.