CLI switch to store signatures using OCI image manifest.

[yizha1]

What is the areas you would like to add the new feature to?

Notation CLI

Is your feature request related to a problem?

OCI artifact manifest was introduced in OCI image spec 1.1.0. Today, not all the registries support OCI artifact manifest, so notation will fail to store signatures to those registries.

What solution do you propose?

Since most registries support OCI image manifest with subject field based on the investigation in this blog https://toddysm.com/2023/01/05/oci-artifct-manifests-oci-referrers-api-and-their-support-across-registries-part-1/, so the proposal is to introduce a switch in notation sign command to provide users an option to store the signatures using OCI image manifest to registries not supporting OCI artifact manifest. This will enable Notation working against most registries.

What alternatives have you considered?

Currently there is no deterministic way to determine what kinds of manifest support by the registries. Before a solution is developed to detect registry capabilities from API level, providing an option for users to choose is the best choice.

Any additional context?

No response