Unclear requirement when setting IShipment.ShippingAddress

Description

Steps to reproduce:
var order = _orderRepository.Service.Create<IPurchaseOrder>("Test");
order.GetFirstShipment().ShippingAddress = order.CreateOrderAddress();

This code does not work because the address is required to have an Id.

Expected:
The CreateOrderAddress method should have an overload that takes the name of the address.

Reported from: http://world.episerver.com/forum/developer-forum/Episerver-Commerce/Thread-Container/2017/8/11-1-failure-to-set-shippingaddress-on-purchaseorder/?pageIndex=1#reply