// that the Assigned config is stable and correct.
  // This is currently implemented as a 10-minute soak period starting when the local
  // record of Assigned config is updated. If the Assigned config is Active at the end
  // of this period, it becomes the LastKnownGood. Note that if Spec.ConfigSource is
  // reset to nil (use local defaults), the LastKnownGood is also immediately reset to nil,