Changing HTTP Statuscode from 200 to 204 for endpoints with not defined response bodies

[janpmeyer]

In the specification for the HTTP-Bindings of the Contract Negotiation and TransferProcess exists some endpoints with no specified response body. (Endpoints are listed at the bottom, Contract Negotiation, Transfer Process)
A clean solution is to introduce an empty response body and change the expected status code from 200 to 204.

Contract Negotiation Provider:
negotiations/:id/request
negotiations/:id/events
negotiations/:id/agreement/verification
negotiations/:id/termination

Contract Negotiation Consumer:
negotiations/:id/offers
negotiations/:id/agreement
negotiations/:id/events

Transfer Process:
transfers/:id/start
transfers/:id/completion
transfers/:id/termination
transfers/:id/suspension

[sebbader-sap]

Thanks @janpmeyer for raising this topic, we have discussed it in our working group call today. We agree that 204 is better and will change the document accordingly soon.

[sebbader-sap]

We just need to figure out if the descriptions in https://www.rfc-editor.org/rfc/rfc9110#name-204-no-content conflict with the intended state transitions.

[sebbader-sap]

It's a little bit late to introduce such changes (our fault), however, I have prepared an PR for it to speed up the discussion.

[sebbader-sap]

Any reason why a response body (and thereby 200) would be required? If not, a 204 certainly reduces confusion.