[FIX] mrp: Unbuild multi serial number components

Use case to reproduce:
- Create a product with a BOM that use at least
twice the same component tracked by SN
- Build this product with SN 'A' and SN 'B'
- Unbuild it
-> Constraint error on duplicate SN

It happens because the unbuild order will create only
one stock.move.lots for SN A with a quantity of 2.

This commit create a stock.move.lots by quant used,
for example if the MO used 2 quants with a qty of 1
and one with lot 'A' and the other with lot 'B'. It will
create 2 stock.move.lots with lots 'A' and 'B'.

Still a know issue: If the user try to unbuild twice
the same MO it will reuse the same unbuilded componenets
than the first unbuild order.

addons/mrp/models/mrp_unbuild.py

@@ -121,14 +121,20 @@ class MrpUnbuild(models.Model):
         for produce_move in produce_moves:
             if produce_move.has_tracking != 'none':
                 original = original_quants.filtered(lambda quant: quant.product_id == produce_move.product_id)
-                if original and not original[0].lot_id:
+                if not original:
                     raise UserError(_("You don't have in the stock the required lot/serial number for %s .") % (produce_move.product_id.name,))
-                self.env['stock.move.lots'].create({
-                    'move_id': produce_move.id,
-                    'lot_id': original[0].lot_id.id,
-                    'quantity_done': produce_move.product_uom_qty,
-                    'quantity': produce_move.product_uom_qty
-                })
+                quantity_todo = produce_move.product_qty
+                for quant in original:
+                    if quantity_todo <= 0:
+                        break
+                    move_quantity = min(quantity_todo, quant.qty)
+                    self.env['stock.move.lots'].create({
+                        'move_id': produce_move.id,
+                        'lot_id': quant.lot_id.id,
+                        'quantity_done': produce_move.product_id.uom_id._compute_quantity(move_quantity, produce_move.product_uom),
+                        'quantity': produce_move.product_id.uom_id._compute_quantity(move_quantity, produce_move.product_uom),
+                    })
+                    quantity_todo -= move_quantity
             else:
                 produce_move.quantity_done = produce_move.product_uom_qty
         produce_moves.move_validate()