Extend ResponseError interceptor body parsing capabilities

This would solve...

ResponseError interceptor adds the body to the error only if the content type is application/json or text/plain. However, some APIs may have more uncommon content types (for example, they may return text/xml. There are also some more exotic ones: meta sends text/javascript whenever the accept header is missing in the request, and Contentful CMS Management APIs use application/vnd.contentful.management.v1+json, even if there's JSON in the responses).

In these scenarios, ResponseError does not include the body and returns an empty string.

The implementation should look like...

ResponseError may expose a parseBody hook so that, without adding complexitiy to Undici itself, users may add custom extraction/parsing whenever needed.

I have also considered...

Additional context

Start by locating the ResponseError interceptor implementation and its current body parsing logic. Define how a parseBody hook should handle uncommon content types without changing existing JSON or text behavior, then add coverage for custom parsing and verify the response body is included in the error.