feat: added shop models

shop/utils.py

@@ -0,0 +1,29 @@
+from decimal import Decimal
+from shop.models import OrderLine, Tax, Product, Order
+from django.db.models import QuerySet
+
+
+def create_order_line_for_product(product: Product, quantity: Decimal, tax: Tax):
+    price = product.prices.last().price
+    base_total = round(price * quantity, 2)
+    taxes = round(base_total * (tax.value / Decimal("100")), 2)
+
+    return OrderLine.objects.create(
+        product=product,
+        quantity=quantity,
+        price=price,
+        base_total=base_total,
+        tax_value=tax.value,
+        taxes=taxes,
+        total=base_total + taxes,
+    )
+
+
+def create_order(lines: QuerySet):
+    order = Order.objects.create()
+
+    for line in lines.all():
+        order.lines.add(line)
+
+    order.calculate_total_from_lines()
+    return order