make Refilling.payment_method a SmallIntegerField

counter/apps.py

@@ -24,12 +24,6 @@
 from django.apps import AppConfig
 from django.utils.translation import gettext_lazy as _
 
-PAYMENT_METHOD = [
-    ("CHECK", _("Check")),
-    ("CASH", _("Cash")),
-    ("CARD", _("Credit card")),
-]
-
 
 class CounterConfig(AppConfig):
     name = "counter"