In many situations, it can be problematic when user add line items to an existing EDI orders that come through the Sales Order import. This is because the line items can have attributes, sometimes notes that are needed to send back with the outgoing EDI document (e.g. 856, 810).

On the other hand, in some exception scenario, certain trading partners may place phone orders and require to send 810 invoice EDI document.

To handle this, we should add an EDI partner flag "Prevent Adding Line Items for EDI Orders?" The default is "Y". But with some EDI partners who place phone order, this flag should be set to "N"