message: Include links to code describing the subprotocol
diff: @@ -121,8 +121,11 @@ impl Client {
  if let Some(auth_header) = self.config.get_auth_header().await? {
  parts.headers.insert(http::header::AUTHORIZATION, auth_header);
  }
  - // Use the binary subprotocol v4.
  - // v4 is the current and sends JSON `metav1.Status` to `error` channel.
  + // Use the binary subprotocol v4, to get JSON `Status` object in `error` channel (3).
  + // There's no official documentation about this protocol, but it's described in
  + // [`k8s.io/apiserver/pkg/util/wsstream/conn.go`](https://git.io/JLQED).
  + // There's a comment about v4 and `Status` object in
  + // [`kublet/cri/streaming/remotecommand/httpstream.go`](https://git.io/JLQEh).
  parts.headers.insert(
  "sec-websocket-protocol",
  "v4.channel.k8s.io".parse().expect("valid header value"),
  