[FIX] mrp_subcontracting_dropshipping: technical fields should not trigger UserError

As a display line does not need to fulfill the dropship check, we skip those
and we do give the user a hint which lines are potentially not fulfilling
the check.

Reproduce:
- Create a purchases order with a picking type for dropshipping
- Add a different destination address (i.e. of another subcontractor to follow up the next manufacturing process)
- Add products with a defined BoM with type subcontractor and vendor
- Additionally add a section or a note
- Try to confirm the purchase order

Result:
- A user error will be triggered about a line which does not fit the current use case

Solution:
- as a section or a note should not be checked we do not trigger for those
- for other products which do not fit the use case we let the user know which lines are blocking

closes odoo/odoo#115044

X-original-commit: 5ba435d1ece208453fc73993b8018c68bb5f889d
Signed-off-by: Arnold Moyaux (arm) <arm@odoo.com>

addons/mrp_subcontracting_dropshipping/models/purchase.py

@@ -31,14 +31,17 @@ class PurchaseOrder(models.Model):
             return super()._get_destination_location()
 
         in_bom_products = False
-        not_in_bom_products = False
+        not_in_bom_products = self.env['purchase.order.line']
         for order_line in self.order_line:
             if any(bom_line.bom_id.type == 'subcontract' and self.dest_address_id in bom_line.bom_id.subcontractor_ids for bom_line in order_line.product_id.bom_line_ids.filtered(lambda line: line.company_id == self.company_id)):
                 in_bom_products = True
-            else:
-                not_in_bom_products = True
+            elif not order_line.display_type:
+                not_in_bom_products |= order_line
         if in_bom_products and not_in_bom_products:
-            raise UserError(_("It appears some components in this RFQ are not meant for subcontracting. Please create a separate order for these."))
+            raise UserError(
+                _("It appears some components in this RFQ are not meant for subcontracting. Please create a separate order for these.") +
+                '\n\n' + '\n'.join(not_in_bom_products.mapped('name'))
+            )
         elif in_bom_products:
             return self.dest_address_id.property_stock_subcontractor.id
         return super()._get_destination_location()