Don't create refunds for payments with negative amounts
Fixes #5257
Cleanup of #5166

Don't rescue exceptions

order shipments in admin by created_at

Raise an exception if an item can't be added

Previously this could fail silently without adding an item to the order.

Remove unnecessary stock check

If stock is unavailable an error will be triggered anyways rolling back
the transaction.

api/shipments: simplify load_transfer_params

Closes #5259