Add cart model
Add cart_token to store in a cookie
Partial index for carts to have a unique cart token
Create cart token
User link to carts
change current_cart retrieval
Move build_cost to products controller from costable concern
Rewrite cart helper for new “cart as an order” system
LineItem copies cost from product on save
Order changes class when status changes to/from cart
Changing order status changes type
Make sure bad cookies only cause one db lookup
Begin redesign of cart controller