anchor.diff:       */
       Future GetPromotionDetails(String code) {
           return Request('register/'+Event+'/promotion', 'GET', {
  -            'code': code
  +            'promo': code
           });
       }
   
  
positive.code:             'first_names': registrations.map((r)=>r.FirstName),
              'last_names': registrations.map((r)=>r.LastName),
              'emails': registrations.map((r)=>r.Email),
              'code': promoCode
          });
      }
  
  
negative.code:     }
  
      return _api;
  }
  