`x509keypairleaf=0`.

Go 1.23 changed
[`net/http.ServeContent`](/pkg/net/http#ServeContent),
[`net/http.ServeFile`](/pkg/net/http#ServeFile), and
[`net/http.ServeFS`](/pkg/net/http#ServeFS) to
remove Cache-Control, Content-Encoding, Etag, and Last-Modified headers
when serving an error. This behavior is controlled by
the [`httpservecontentkeepheaders` setting](/pkg/net/http#ServeContent).

pkg net/http, func Redirect(ResponseWriter, *Request, string, int)
pkg net/http, func RedirectHandler(string, int) Handler
pkg net/http, func Serve(net.Listener, Handler) error
pkg net/http, func ServeContent(ResponseWriter, *Request, string, time.Time, io.ReadSeeker)
pkg net/http, func ServeFile(ResponseWriter, *Request, string)
pkg net/http, func SetCookie(ResponseWriter, *Cookie)
pkg net/http, func StatusText(int) string