Add filtering not refunded in ticket type

Author: emscb

ticket/models.py

@@ -32,10 +32,10 @@ def buyable(self) -> bool:
         """잔여 수량이 있는지"""
         sat_ticket_count = Ticket.objects.filter(
             models.Q(ticket_type__day="SAT") | models.Q(ticket_type__day="WEEKEND")
-        ).count()
+        ).filter(is_refunded=False).count()
         sun_ticket_count = Ticket.objects.filter(
             models.Q(ticket_type__day="SUN") | models.Q(ticket_type__day="WEEKEND")
-        ).count()
+        ).filter(is_refunded=False).count()
 
         can_buy_sat_ticket = sat_ticket_count < config.CONFERENCE_PARTICIPANT_COUNT_SAT
         can_buy_sun_ticket = sun_ticket_count < config.CONFERENCE_PARTICIPANT_COUNT_SUN