Today, a user who tries pushing content to a capsule will see the following:

$ podman push 66640e9653de centos9-proxy-devel.manicotto.example.com/test
Getting image source signatures
Error: trying to reuse blob sha256:b7d21803af9eaacfb7366f81ad3fe055198f7e0029de30af8e38fd4df02897aa at destination: checking whether a blob sha256:b7d21803af9eaacfb7366f81ad3fe055198f7e0029de30af8e38fd4df02897aa exists in centos9-proxy-devel.manicotto.example.com/test: authentication required

It is not clear that the container gateway does not support pushing content. We should accept the blob check that is failing with an auth error here and then deny PUT/PATCH/POST requests as necessary and return an 'unsupported' error.