feat(configurator): per-line lot pricing (derive unit price, keep qty)

fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_line.py

@@ -238,6 +238,21 @@ class FpDirectOrderLine(models.Model):
         string='Unit Price',
         currency_field='currency_id',
     )
+    is_lot_priced = fields.Boolean(
+        string='Lot Price',
+        help='Price the whole quantity as a flat lot total instead of '
+             'per unit. Unit price is derived = lot total / quantity; '
+             'the quantity is preserved for production.',
+    )
+    lot_total = fields.Monetary(
+        string='Lot Total', currency_field='currency_id',
+    )
+
+    @api.onchange('is_lot_priced', 'lot_total', 'quantity')
+    def _onchange_lot_pricing(self):
+        for line in self:
+            if line.is_lot_priced and line.quantity:
+                line.unit_price = (line.lot_total or 0.0) / line.quantity
     line_subtotal = fields.Monetary(
         string='Subtotal',
         currency_field='currency_id',