defaults to `x509keypairleaf=1`. Previous versions default to
`x509keypairleaf=0`.
This setting will be removed in Go 1.27.

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