Set "Content-Length" header for response(...).emtpy()

[christoph-fricke]

openapi-fetch skips parsing the response body when the status code is 204 or the content-length header is 0 (Source Code). For other status codes (like 201), request handlers have to explicitly set the content-length header when creating empty responses to avoid JSON parsing errors in openapi-fetch.

response(201).empty({ headers: { 'Content-Length': '0' } })

When using HttpResponse.json() or HttpResponse.text() MSW calculates the content-length. Otherwise, the header is not calculated implicitly for every response.
For a better developer experience we should set the content-length header implicitly as well, when empty responses are created. This avoids confusing problems when using response(201).empty().