Entity: CartItem

Represents a product entry in a cart with its quantity.

Fields

Field	Type	Nullable	Default	Description
id	serial	no	auto	Primary key
cart_id	integer	no	—	FK to cart.id
product_id	integer	no	—	FK to product.id
quantity	integer	no	—	Number of units (min 1)

Standard columns (created_at, updated_at, deleted_at) are inherited per ADR-007 and should not be listed here.

Relations

Relation	Type	Target entity	FK	On delete
cart	many-to-one	Cart	cart_item.cart_id	cascade
product	many-to-one	Product	cart_item.product_id	restrict

Business rules

• quantity must be at least 1.
• A product can appear only once per cart. Adding the same product again updates the quantity by summing the values.