Improve age management for getting products and make get_product a part of counter model

counter/models.py

@@ -659,6 +659,34 @@ class Counter(models.Model):
         # but they share the same primary key
         return self.type == "BAR" and any(b.pk == customer.pk for b in self.barmen_list)
 
+    def get_products_for(self, customer: Customer) -> list[Product]:
+        """
+        Get all allowed products for the provided customer on this counter
+        Prices will be annotated
+        """
+
+        products = self.products.select_related("product_type").prefetch_related(
+            "buying_groups"
+        )
+
+        # Only include age appropriate products
+        age = customer.user.age
+        if customer.user.is_banned_alcohol:
+            age = min(age, 17)
+        products = products.filter(limit_age__lte=age)
+
+        # Compute special price for customer if he is a barmen on that bar
+        if self.customer_is_barman(customer):
+            products = products.annotate(price=F("special_selling_price"))
+        else:
+            products = products.annotate(price=F("selling_price"))
+
+        return [
+            product
+            for product in products.all()
+            if product.can_be_sold_to(customer.user)
+        ]
+
 
 class RefillingQuerySet(models.QuerySet):
     def annotate_total(self) -> Self: