code: func GetEtcdPeerAltNames(cfg *kubeadmapi.InitConfiguration) (*certutil.AltNames, error) {
  	return getAltNames(cfg, kubeadmconstants.EtcdPeerCertName)
  }
docs: // GetEtcdPeerAltNames builds an AltNames object for generating the etcd peer certificate.
  // Hostname and `API.AdvertiseAddress` are included if the user chooses to promote the single node etcd cluster into a multi-node one (stacked etcd).
  // The user can override the listen address with `Etcd.ExtraArgs` and add SANs with `Etcd.PeerCertSANs`.