Easy shipment cost on shipment
The shipment costs are computed with on_change
calls so this makes harder to enter a self-computed value as it may be erased on any change later.
Also the on_change
calls may not always be triggered to update the computation (ex: shipment with same storage than output, inventory moves are not filled).
So I think we should have an edit check box like for the delivery date on purchase line. But also the computed value if not edited should be stored once the shipment is done as the carrier setup may change in the future.