[FIX] pos_online_payment: prioritize pos order customer

Before this commit:
POS online payments uses the logged-in user or the public user,
even when a POS order customer might also be present.

After this commit:
We check the partner_id for POS orders and give it
precedence over both the logged-in user and the public user.

task-3805695

closes odoo/odoo#157562

Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>

addons/pos_online_payment/controllers/payment_portal.py

@@ -99,7 +99,7 @@ class PaymentPortal(payment_portal.PaymentPortal):
 
         user_sudo = request.env.user
         logged_in = not user_sudo._is_public()
-        partner_sudo = self._get_partner_sudo(user_sudo)
+        partner_sudo = pos_order_sudo.partner_id or self._get_partner_sudo(user_sudo)
         if not partner_sudo:
             return self._redirect_login()
 
@@ -179,7 +179,7 @@ class PaymentPortal(payment_portal.PaymentPortal):
         exit_route = request.httprequest.args.get('exit_route')
         user_sudo = request.env.user
         logged_in = not user_sudo._is_public()
-        partner_sudo = self._get_partner_sudo(user_sudo)
+        partner_sudo = pos_order_sudo.partner_id or self._get_partner_sudo(user_sudo)
         if not partner_sudo:
             return self._redirect_login()