Add Item to Shopcart

[yuhao0308]

As a customer, I need to be able to add a product to my shopcart by specifying the product ID, quantity, and product description, So that I can collect the products I wish to purchase in one place.

Assumptions:

• The customer has an active shopcart associated with their customer ID.
• The product ID, description, and quantity are valid inputs.
• API endpoint: POST /shopcarts/{id}/items <- Create a new item in a shopcart

Acceptance Criteria:

Given that a customer has an active shopcart,
When they add a product with a valid product ID, description, and quantity,
Then the product is added to the shopcart, and the shopcart reflects the new product.

Given that a product is already in the cart,
When the customer adds the same product,
Then the quantity of the product is updated in the shopcart.

[safipatel]

Added API endpoint that this covers for clarity