[FIX] pos_loyalty: fix data format of reward_id in the pos_restaurant

Previously, reward_id was an array of two elements containing
the ID and name of the reward. But in the frontend,
reward_id is supposed to be an int with the ID

Adaptation of the _prepare_order_line function in the following modules:
- point_of_sale
- pos_restaurant
- pos_loyalty

Now the data is correctly sent to the frontend and the error
is no longer present.

closes odoo/odoo#111048

Signed-off-by: Heinz Robin (rhe) <rhe@odoo.com>

addons/point_of_sale/models/pos_order.py

@@ -1045,6 +1045,9 @@ class PosOrder(models.Model):
         """This function is here to be overriden"""
         return []
 
+    def _prepare_order_line(self, order_line):
+        return order_line
+
     def export_for_ui(self):
         """ Returns a list of dict with each item having similar signature as the return of
             `export_as_JSON` of models.Order. This is useful for back-and-forth communication

addons/pos_loyalty/models/pos_order.py

@@ -143,6 +143,14 @@ class PosOrder(models.Model):
             'coupon_report': coupon_per_report,
         }
 
+    def _prepare_order_line(self, order_line):
+        order_line = super(PosOrder, self)._prepare_order_line(order_line)
+
+        if order_line["reward_id"]:
+            order_line["reward_id"] = order_line["reward_id"][0]
+
+        return order_line
+
     def _get_fields_for_order_line(self):
         fields = super(PosOrder, self)._get_fields_for_order_line()
         fields.extend(['is_reward_line', 'reward_id', 'coupon_id', 'reward_identifier_code', 'points_cost'])

addons/pos_restaurant/models/pos_order.py

@@ -73,6 +73,7 @@ class PosOrder(models.Model):
         :type order_line: pos.order.line.
         :returns: dict -- dict representing the order line's values.
         """
+        order_line = super(PosOrder, self)._prepare_order_line(order_line)
         order_line["product_id"] = order_line["product_id"][0]
         order_line["server_id"] = order_line["id"]