Move private endpoint logic to v2 model

Separate v2 model code into the actual v2 model class. Introduce a v2
model test to exercise that code.
Merge pull request #19 from ironcladlou/cart-refactor

Move private endpoint logic to v2 model
Fix typo
Pass skip_hooks to cart_model.destroy

Change ApplicationContainer to pass skip_hooks to cart_model.destroy.
V2 Strategy still needs to honor this flag.
wip: mark v2 apps