Reassign pricing on quantity change [#87553]

Includes spec cleanup and updates to set price policies and price groups for `OrderDetail#reassign_price` to succeed.

The reported issue stemmed from a quantity change through the attribute update in `AccessoriesController#update_accessories`, where price recalculation wouldn't happen.

With this `before_save` hook, I'm wondering if `OrderDetail#update_quantity` needs to exist anymore (same goes for `OrderDetail#update_account`).