Cart rendering, bug fixes with cart adding/rming

dto/__init__.py

@@ -0,0 +1,3 @@
+from .cart import CartItemDTO
+
+__all__ = ["CartItemDTO"]

dto/cart.py

@@ -0,0 +1,19 @@
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class CartItemDTO:
+    product_id: int
+    name: str
+    quantity: int
+    price: int
+
+    @property
+    def total(self):
+        return self.price * self.quantity
+
+
+@dataclass
+class CartDTO:
+    items: list[CartItemDTO]
+    total: int