https://greenbytes.de/tech/webdav/rfc7231.html#rfc.section.4.3.7.p.4:

A server MUST generate a Content-Length field with a value of "0" if no payload body is to be sent in the response.

That is incorrect, as the status code could be 204, or the response might come with chunked encoding (even when empty).

This ishttps://www.rfc-editor.org/errata/eid5806.