Thanks for the PR! Just to give you a heads up, it's very unlikely this will snuck in into the v3 stable release (no plan on ETA) due to the blast radius of this change. I just want to set the expectations here!

@milosgajdos Completely understand. My main motivation for this was to see if I could implement the API . which if you are interested in a unfinished version is located here

Could I suggest that a way to include the subject functionality before the v3 could be to include it as a experimental feature. Effectively this proposal would add the following to the config yaml

experiments:
   subjects: true

The api and write paths could then both be implemented behind the feature flag providing the ability to incrementally deliver this solution without releasing. Users would be able to enable it at their own risk.

This is obviously your decision to make. I know that projects like harbor implement the subject functionality independently of the registry itself so it might be useful in the future to provide that feature flag regardless.

This change is required to implement the referer API in a consuming application I maintain. Is there a better alternative than waiting or vendoring the code in our application?

Maybe some other OSS implementation provider referrer API implementation but it's not currently planned in upstream. First we want to make a stable release and then discuss what next if anything. There has been no support from CNCF and negligible activity from most of the maintainers, so I would not rely / wait for this

Thanks for the re-base and the work @alistair. I've moved to a role that doesn't deal with the registry much any more. So the chances of me getting this across the line is slim. Anyone else is welcome to pick this up or do it green field.

This is failing CI