File: /includes/class-shopping-cart.php Session Key: agency_pulse_cart Coupon Key: agency_pulse_coupon Methods:
                
                    add_to_cart($product_id, $quantity) - Add item to session cart
                    remove_from_cart($product_id) - Remove item from cart
                    update_quantity($product_id, $quantity) - Change item quantity
                    clear_cart() - Empty entire cart (after order)
                    get_cart_count() - Get total item count
                    set_coupon($coupon_data) - Apply discount coupon
                    get_coupon() - Retrieve applied coupon
                    clear_coupon() - Remove applied coupon add_to_cart($product_id, $quantity) - Add item to session cart remove_from_cart($product_id) - Remove item from cart