Add product into cart
delete item from cart
fix price calculating bug
update TODO. complete deletion of items in cart
users are able to switch the quantity of cart items
User is able to add product and see the order page
Add token to order
user is able to checkout order
after convert cart to order, clean up the cart
user is able to browse its orders
add AASM
add state settings
chage items of navigation bars
add state actions at front and backend, user is able to check state at their order list.