code: def should_show_thanks_page_to(participant):
      
      if participant is None:
          return False
      status = participant.status
      marked_done = participant.end_time is not None
      ready_for_external_submission = (
          status in ("overrecruited", "working") and marked_done
      )
      assignment_complete = status in ("submitted", "approved")
  
      return assignment_complete or ready_for_external_submission
docs: In the context of the /ad route, should the participant be shown
      the thanks.html page instead of ad.html?