// empty string if the object was updated through the main resource. The
  // value of this field is used to distinguish between managers, even if they
  // share the same name. For example, a status update will be distinct from a
  // regular update using the same manager name.
  // Note that the APIVersion field is not related to the Subresource field and
  // it always corresponds to the version of the main resource.
  optional string subresource = 8;
}