Before being able to switch MBS itself to UMB, we need to enable/configure the protonmsg plugin for Kojihub : https://docs.pagure.org/koji/plugins/#proton-messaging

So as a dependency, we should have first the cert/topic to use, and we can then verify that sending from kojihub to umb works. (CS-2586)

After that, we'll be able to make umb consume these messages (watch/sub) but also send itself to topics