As a customer I want to be able to update/remove items from my cart

[valincius]

Given I am a customer
When I navigate to the cart
Then I want to be able to change the quantity of each product in my cart
And I want to be able to remove a product from my cart

• Add number input & button beside each line item to manage the quantity/remove item from cart
  • Can update the existing add-to-cart endpoint to also handle removing an item