Many registries in corporate environments are behind proxies and/or load-balancers, some of which may strip the Docker-Content-Digest header for some (or all) media-types. Additionally, some registries may not send the header at all (see related issue #3792 for context).

As a result, storing manifests may fail. This is an issue for users of the library (such as oc-mirror) which check if an error is returned but only validate the digest header on manifest push if it is returned.