code: func MarshalAuthorizedKeysFormat(clusterName string, keyBytes []byte) (string, error) {
  	comment := url.Values{
  		"type":        []string{"user"},
  		"clustername": []string{clusterName},
  	}
  
  	return fmt.Sprintf("cert-authority %s %s", strings.TrimSpace(string(keyBytes)), comment.Encode()), nil
  }
docs: // MarshalAuthorizedKeysFormat returns the certificate authority public key exported as a single
  // line that can be placed in ~/.ssh/authorized_keys file. The format adheres to the
  // man sshd (8) authorized_keys format, a space-separated list of: options, keytype,
  // base64-encoded key, comment.
  // For example:
  //
  //    cert-authority AAA... type=user&clustername=cluster-a
  //
  // URL encoding is used to pass the CA type and cluster name into the comment field.