[FIX] point_of_sale: keep refunded line when going back to floor plan

Current behavior:
In PoS restaurant, if you refund an order and go back to the floor plan,
before validating the refund, the link between the original order and
the refund is lost.

Steps to reproduce:
- Open PoS restaurant
- Create an order
- Refund the order but do not validate it
- Go back to the floor plan, and go back on the order
- Validate the refund
- Close the session
- Go on the orders, you will see that the refund has no link to the
  original order

opw-3202383

closes odoo/odoo#116748

X-original-commit: 3ea9a8a0b3a9085b35314633e56bb7e508df7008
Signed-off-by: Trinh Jacky (trj) <trj@odoo.com>
Signed-off-by: Engels Robin (roen) <roen@odoo.com>

addons/pos_restaurant/models/pos_order.py

@@ -30,6 +30,10 @@ class PosOrder(models.Model):
             'note',
             'uuid',
             'mp_skip',
+            'full_product_name',
+            'customer_note',
+            'price_extra',
+            'refunded_orderline_id',
         ])
         return fields