Fix related_name issue in foreignkeys.
Add DeliveryOptionAdmin.
Add __hash__ and __eq__ to Store model, and make slug be unique.
Add in_effect property to DeliveryOption model.
Use store_items instead of list of item for cart view.
Show cart store summary with delivery options.
Adjust cart view and form layout.
Check store instread of store.slug, and check type before eq.
Refactor new_from_cart view to fit new DeliveryWindow model.
Show delivery_window time in local time zone.
Format datetime in 24h.
Correct the time_zone setting.
Add CheckoutForm for easier server-side form validation.
Add datetime to context for client side datetime validation.
Display paypal form in show_invoice view.
Use CheckoutForm to generate cart page and handle checkout in same view.
Add cost field to DeliveryOption model.
Rename shipping to delivery in Invoice model.