[Feature Request] API endpoint to determine the backend repo without authentication

[cmgorton]

Request: A public API endpoint that returned the backend registry being used by a given package UUID.

We currently have this endpoint /api/v1/packages/{id} but it requires authentication.

Linuxserver would like for their mods to determine the backend repo without authentication (or using a different auth method) because any auth token would have to be stored with the mod which is user-visible.

Extra information: They have said it doesn't need to be the full URL, or any other package info. A dockerhub/ghcr/quay/etc value would be sufficient, but they don't want to be to prescriptive.