public IEnumerable <RowLoadResult> GetRowsMissingFrom(TableLoadResult other)
 => Rows.Where(_ => other.GetRowWithMatchingIdentifier(_) == null);
 public IEnumerable <RowLoadResult> GetRowsWhereFieldsDifferFromMatchIn(TableLoadResult other)
 => Rows.Where(_ => other.Rows.Any(row => row.HasSameIdentifier(_) &&
                                   row.HasDifferentFieldValues(_)));