[FIX] fleet: Assign internal user as driver

With a user with only Fleet Administrator rights.
Assign an internal user as the driver of a vehicle (other than the
current user) => access error, you cannot write on model `res.user`.

Writing on a partner linked to an internal user requires write access to
this user.

closes odoo/odoo#47505

Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

addons/fleet/models/fleet_vehicle.py

@@ -208,7 +208,7 @@ class FleetVehicle(models.Model):
             res.create_driver_history(vals['driver_id'])
         if 'future_driver_id' in vals and vals['future_driver_id']:
             future_driver = self.env['res.partner'].browse(vals['future_driver_id'])
-            future_driver.write({'plan_to_change_car': True})
+            future_driver.sudo().write({'plan_to_change_car': True})
         return res
 
     def write(self, vals):
@@ -218,7 +218,7 @@ class FleetVehicle(models.Model):
 
         if 'future_driver_id' in vals and vals['future_driver_id']:
             future_driver = self.env['res.partner'].browse(vals['future_driver_id'])
-            future_driver.write({'plan_to_change_car': True})
+            future_driver.sudo().write({'plan_to_change_car': True})
 
         res = super(FleetVehicle, self).write(vals)
         if 'active' in vals and not vals['active']:
@@ -248,7 +248,7 @@ class FleetVehicle(models.Model):
         vehicles._close_driver_history()
 
         for vehicle in self:
-            vehicle.future_driver_id.write({'plan_to_change_car': False})
+            vehicle.future_driver_id.sudo().write({'plan_to_change_car': False})
             vehicle.driver_id = vehicle.future_driver_id
             vehicle.future_driver_id = False