[api] line items now receive save in this test
[frontend] Persist line item in orders_controller_spec
[frontend] Save an order in OrdersController#update after update_cart is called
[frontend] Work with in-memory objects for eligible shipment adjustments in checkout/_summary
[frontend] Correct definition for eligible_promotion_adjustments in _order_details
omg
[api] Save an order after applying a coupon code

The Handler will create a non-persisted Adjustment record, and saving the record will save the adjustment and persist the totals.
Only save the order once in OrderContents#update