Add products to cart

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Description: As a shopper, I want to be able to add products to my cart so that I can review and purchase them later.

Acceptance Criteria:

1. Display a list of products available for purchase on the website.
2. Include an "Add to Cart" button or icon next to each product.
3. When I click the "Add to Cart" button for a product, the product should be added to my shopping cart.
4. The cart should display the added products, including their names, quantities, prices, and a subtotal for each item.
5. Allow me to adjust the quantity of each product in the cart or remove products from the cart.
6. Calculate and display the total cost of the items in the cart.
7. Provide clear visual feedback when a product is successfully added to the cart.
8. Ensure that the cart contents are persisted across different pages or sessions, so I can continue shopping from where I left off.
9. Implement proper error handling and validation to prevent adding unavailable or invalid products to the cart.
10. Create unit tests to verify the functionality of adding products to the cart.

Definition of Done:

• The product list is displayed on the website.
• An "Add to Cart" button or icon is included next to each product.
• Clicking the "Add to Cart" button adds the product to the cart.
• The cart displays added products with names, quantities, prices, and subtotals.
• I can adjust the quantity or remove products from the cart.
• The total cost of items in the cart is calculated and displayed.
• Visual feedback is provided for successful product additions.
• Cart contents are persisted across pages or sessions.
• Error handling and validation are implemented and tested.
• Unit tests for adding products to the cart pass successfully.
• Code is reviewed and approved.