After building the product catalog, the next step is to create a shopping cart so that users can pick the products that they want to purchase. A shopping cart allows users to select products and set the amounts they want to order, and then store this information temporarily, while they browse the site until they eventually place an order. The cart has to be persisted in the session so that the cart items are maintained during the user's visit.

We will use Django's session framework to persist the cart. The cart will be kept in the session until it finishes or the user checks out of the cart. We will also need to build additional Django models for the cart and its items.