Switch to OCI media types.

[dlorenc]

No description provided.

[dlorenc]

cc @jdolitsky we should figure out how to get this in.

[dlorenc]

Would it make sense to register a media type somewhere?

[jdolitsky]

Strictly speaking, the OCI artifacts project says to register one with IANA. In reality, I don't know of any project has gone through with that process..

That being said, I do think it makes sense for this project to define a custom mediatype. See https://github.com/opencontainers/artifacts/blob/master/artifact-authors.md#defining-a-unique-artifact-type

So something along the lines of:

application/vnd.sigstore.cosign.config.v1+json

This could just be published in the cosign docs somewhere.

For registries that only allow Docker, perhaps provide a bool flag such as --as-docker, or make it even more customizable with a string flag/env var.

[dlorenc]

We fixed this in #300