[FIX] delivery: onchange_carrier

Steps to reproduce:

- Create a Sales Order with 2 product qty
- Keep Delivery Method as DHL International
- Confirm
- Open Delivery Order
- Edit Qty of the Delivery Order
- Change Carrier (any integrated)
- Validate the transfer
- Process the backorder
- Edit and change the Carrier to normal or free delivery charges
- Validate

Bug:
The price of the free delivery charges was not recomputed and kept
the carrier price set on the SO.

Fix:
When the price of the carrier is "fixed" or "base_on_rule", the price must
be reconsidered in case of change.

opw:691224

addons/delivery/models/stock_picking.py

@@ -52,7 +52,7 @@ class StockPicking(models.Model):
                 weight += uom_obj._compute_qty_obj(packop.product_uom_id , packop.product_qty, packop.product_id.uom_id) * packop.product_id.weight
         self.weight_bulk = weight
 
-    carrier_price = fields.Float(string="Shipping Cost", readonly=True)
+    carrier_price = fields.Float(string="Shipping Cost")
     delivery_type = fields.Selection(related='carrier_id.delivery_type', readonly=True)
     carrier_id = fields.Many2one("delivery.carrier", string="Carrier")
     volume = fields.Float(copy=False)
@@ -63,6 +63,11 @@ class StockPicking(models.Model):
     package_ids = fields.Many2many('stock.quant.package', compute='_compute_packages', string='Packages')
     weight_bulk = fields.Float('Bulk Weight', compute='_compute_bulk_weight')
 
+    @api.onchange('carrier_id')
+    def onchange_carrier(self):
+        if self.carrier_id.delivery_type in ['fixed', 'base_on_rule']:
+            self.carrier_price = self.carrier_id.price
+
     @api.depends('product_id', 'move_lines')
     def _cal_weight(self):
         for picking in self: