Editing an order before checking out

Starting with API V7Preview5, it became possible to edit an order immediately before the bill.

Before the order is transferred to the bill, a notification is triggered BeforeOrderBill. Previously, it allowed you to cancel the transfer of an order to status Bill by throwing an OperationCanceledException exception at the appropriate subscriber. It also allowed user interaction (when possible) through IViewManager, show different windows in SyrvePOS.

Now, in addition to everything else, we have added the ability to change the order via IOperationService, made available in the notification arguments. Thus, before fixing the cost, you can edit the composition of dishes or discounts of the order.