DELETE response body not following RFC 9110

[thegagne]

AEP 135 currently states that a delete should return a 204 with a response body of {}.

https://aep.dev/135/#responses

paths:
  /publishers/{publisher_id}/books/{book_id}:
    delete:
      responses:
        '204':
          content:
            application/json:
              schema: {}
          description: Successful response

However, RFC 9110 states that it should have literally no body on a 204.

The 204 (No Content) status code indicates that the server has successfully fulfilled the request and that there is no additional content to send in the response content.
...
A 204 response is terminated by the end of the header section; it cannot contain content or trailers.

Looking at our options for DELETE in section 9.3.5, our options are switch to a 200, or use a 204 with no body at all.

a 202 (Accepted) status code if the action will likely succeed but has not yet been enacted,
a 204 (No Content) status code if the action has been enacted and no further information is to be supplied, or
a 200 (OK) status code if the action has been enacted and the response message includes a representation describing the status.

I think I raised this issue before the 2026 release was finalized and pushed to get this switched to a 204, but didn't realize that a 200 would actually be correct if we had a response body describing the status. I think the question remains - do we need the response body or not, since it doesn't really describe the status.

[toumorokoshi]

Interesting, thanks for investigating it!

I think we agreed upon some body because it did make some parsing logic easier (IIRC there's some proto-json work that would return an empty body).

I'd probably move toward making this a 200 - most clients don't really assert the status code?