Make goods & costs editable/creatable from service page

costs/admin.py

@@ -160,3 +160,13 @@ class ServiceAdmin(admin.ModelAdmin):
 
     def new_subscriber_cost(self, obj):
         return '{:.2f}€'.format(obj.get_prices()['total_goods_value_share'])
+
+
+@admin.register(Good)
+class GoodAdmin(admin.ModelAdmin):
+    pass
+
+
+@admin.register(Cost)
+class CostAdmin(admin.ModelAdmin):
+    pass