API version can be lost when using media type parameters #37619

MediaTypeParamApiVersionResolver supports extracting an API version from Accept or Content-Type.

With the resolver configured for application/json and parameter version, this request resolves to null instead of "3":

Accept: */*
Content-Type: application/json;version=3

Removing Accept resolves the version correctly.

The resolver returns the parameter value from the first compatible Accept media type, even when that value is null. This prevents checking Content-Type. Both MVC and WebFlux are affected.

On the client side, ApiVersionInserter.useMediaTypeParam() adds the version only to an existing Content-Type. The default WebClient connector, Reactor Netty, adds Accept: */*, which triggers the server-side behavior above.

If Content-Type is absent, e.g. for a GET or DELETE request sent without that header, the inserter adds no version and does not write to Accept.

Expected behavior:

• Fall back to Content-Type when no version is found in Accept.
• Support client-side media type version insertion for requests without Content-Type.

Related Issue:

• Add ApiVersionResolver based on parameter in media type #35050
• Add support for MediaType in ApiVersionInserter #35259