code: def get_subdomain_DID_record(self, did):
          
          try:
              did_info = parse_DID(did)
              assert did_info['name_type'] == 'subdomain'
          except Exception as e:
              if BLOCKSTACK_DEBUG:
                  log.exception(e)
  
              return {'error': 'Invalid DID', 'http_status': 400}
  
          subrec = get_DID_subdomain(did, check_pending=True)
          if subrec is None:
              return {'error': 'Failed to load subdomain from {}'.format(did), 'http_status': 404}
  
          return {'record': subrec.to_json()}
docs: Given a DID for subdomain, get the subdomain record
          Return {'record': ...} on success
          Return {'error': ...} on error