Clarify status code usage for malformed stream configurations sent to the configuration endpoint

[thomasdarimont]

In the conformance tests, we send a malformed stream configuration in the request body with a PUT request to the stream configuration endpoint as part of the negative tests to check the error codes.

The SSF spec states under 8.1.1.4. Replacing a Stream's Configuration

- 400 if the request body cannot be parsed, a Transmitter-Supplied property is incorrect, or if the request is otherwise invalid
- 404 if there is no Event Stream with the given “stream_id” for this Event Receiver

In the conformance tests, we currently assume that a malformed stream configuration should result in a 400 HTTP status code.

During the conformance test runs, we saw a few SSF transmitter implementations that return a 404 status here instead of the expected 400, probably due to different order of checks.

Question: Is the SSF spec clear enough at this point, or do we need to include wording in the CAEP interop spec that further clarifies “if the request body cannot be parsed”?