feat: Add v1.Manifest 'artifactType' field from OCI spec

[bmoylan]

OCI has released v1.1.0 of the Image Spec which includes the artifactType field in the manifest json schema: https://github.com/opencontainers/image-spec/blob/v1.1.0/manifest.md#image-manifest-property-descriptions

Relevant to #1832 closed as stale

[bmoylan]

Hi @jonjohnsonjr or @imjasonh any chance you could take a look at this? Thanks!

[cdupuis]

@bmoylan, Thanks for doing the work on this. Any chance to get this into main any time soon? It would be super helpful as we start to see more OCI 1.1 adoption across the ecosystem.

[bmoylan]

👋 Hey @jonjohnsonjr @imjasonh sorry for the pings but it would be great to get this reviewed when possible, thanks!

[kipz]

Yeah, it'd be great to get this in.

[kipz]

@bmoylan I've added a couple of extra bits for better artifactType here: bmoylan#2

• Set artifactType in fallback descriptor (if present)
• Similarly for in-memory registry: set artifactType instead of config mediaType (if present)
• Send artifactType filter to registry if supplied in call to referrers API

[nmiyake]

I noticed this issue as well and it would be great to get this PR merged!

Another issue with regards to diffs between the current implementation and the OCI 1.1 referrers specification is that the specification states that the referrer descriptors MUST have the annotations from the Image or ImageIndex, but currently this library doesn't do that.

I opened PR #1998 to fix the "annotations" issue. I believe that merging these 2 PRs should make go-containerregistry compliant in its behavior.

I didn't see an existing issue for this, so I filed #1997 to explicitly describe the issues.