PATCH maintenance/work-orders: Add support for historical started and archived timestamps

The PATCH maintenance/work-orders endpoint has some new features! Added the following optional fields for backfilling historical work order data:

• startedAtTime - historical time work started on the work order
• archivedAtTime - historical time the work order was archived (closed or cancelled)
  Each field, along with the existing completedAtTime, is now persisted as provided instead of being overwritten by the automatic status-driven timestamp; leave a field unset to keep today's automatic behavior. startedAtTime is also now included on the response.