[FIX] sale_coupon: access to fields on coupon from POS

When a pos launched by a user having no access rights on sales order
lines is launched. It cannot have access to the coupon program because
it tries to get the computed field order_count that needs to read the
sale order lines.

closes odoo/odoo#84544

Task-id: 2742528
Signed-off-by: Masereel Pierre <pim@odoo.com>

addons/sale_coupon/models/coupon_program.py

@@ -12,7 +12,7 @@ class CouponProgram(models.Model):
     # The api.depends is handled in `def modified` of `sale_coupon/models/sale_order.py`
     def _compute_order_count(self):
         for program in self:
-            program.order_count = self.env['sale.order.line'].search_count([('product_id', '=', program.discount_line_product_id.id)])
+            program.order_count = self.env['sale.order.line'].sudo().search_count([('product_id', '=', program.discount_line_product_id.id)])
 
     def action_view_sales_orders(self):
         self.ensure_one()