Sale Carrier default selection if Carrier Cost method is None

Feature
1

Rational

In Sales, Carrier is not selected by default if Shipment cost method is None.
I think some companies who are using a carrier manually will still appreciate automatic selection of carrier, even without using Shipment cost method to add a Shipping line to the Sale.
I think it is useful to store which carrier was used for the Sale.

Proposal

Options as I see it are:

  1. Select Carrier for a sale even if Shipment Cost Method is None
  2. or add another option for shipment cost method: Select Carrier
    I prefeer 1.

Implementation

2

For me the problem is that if there is no shipment cost method, we can not know if there is a carrier to select or not because the shipment can be managed by the customer or it can pick on warehouse.
But if there is a shipment cost method set, then we know for sure that we need a carrier so we can pre-select one.