Description
I would suggest, to make the cli commands a bit more consistent, verbose and failsafe.
Consistency: Some aio-cli commands take "json" files as input, some are interactive. It's better to have both options in all commands. If I had to choose, I'd prefer the non-interactive way - because that can be scripted (e.g. for ci/cd)
Failsafe: If Event-Metadata is mandatory, why not have it created with aio event provider create in one command? If there is a usecase for metadata-less providers, this could be done with a flag in the command (--nometadata) .. everything else will yield an error ("please provide metadata")..
Verboseness: The provider create command could create a hint ("Don't forget to register metadata"); the provider list could have a column for "metadata" or "metadata missing".
Verboseness: When registering an event (listener) and the provider does not have metadata or the event-code to be registered is not provided we should not return a 400-bad request but what specifically went wrong. If the underlying API does not provide that information, the client could provide some hints ("please check if the provider has metadata and it aligns with the event metadata you are registering for")