> Is there any plan to move forward on this issue?
I'd personally still very much like to see progress here; so far no one was ready to pick it up, though. So if you're interested in implementing this, a PR would be more than welcome.
> I think you should also be able to infer or provide a schema for the aggregate ID.
This already should be the case? Do you see a case where the message key schema wouldn't be set? If so, I agree that this should be changed.
Reading the issue again, I'd by now lean towards using regular JSON Schema (https://json-schema.org/
) for describing the payload schema.