// ratio between the target value and the current value by the current
  // number of pods.  Ergo, metrics used must decrease as the pod count is
  // increased, and vice-versa.  See the individual metric source types for
  // more information about how each type of metric must respond.
  // +optional
  repeated MetricSpec metrics = 4;
}

//  1. Ignored fields.  It includes many fields which are not generally honored.  For instance, ResourceVersion and FieldPath are both very rarely valid in actual usage.
//  2. Invalid usage help.  It is impossible to add specific help for individual usage.  In most embedded usages, there are particular
//     restrictions like, "must refer only to types A and B" or "UID not honored" or "name must be restricted".
//     Those cannot be well described when embedded.