repeated string ipFamilies = 19;

  // IPFamilyPolicy represents the dual-stack-ness requested or required by
  // this Service. If there is no value provided, then this field will be set
  // to SingleStack. Services can be "SingleStack" (a single IP family),
  // "PreferDualStack" (two IP families on dual-stack configured clusters or
  // a single IP family on single-stack clusters), or "RequireDualStack"

- Add dual-stack Services (alpha).  This is a BREAKING CHANGE to an alpha API.
  It changes the dual-stack API wrt Service from a single ipFamily field to 3
  fields: ipFamilyPolicy (SingleStack, PreferDualStack, RequireDualStack),
  ipFamilies (a list of families assigned), and clusterIPs (inclusive of
  clusterIP).  Most users do not need to set anything at all, defaulting will

    * Notes on LB name:
    * to ensure backword and forward compat:
    * - SingleStack -v4 (pre v1.16) => BackendPool name == clusterName
    * - SingleStack -v6 => BackendPool name == clusterName (all cluster bootstrap uses this name)
    * DualStack:
    * => IPv4 BackendPool name == clusterName