[FIX] website_sale: auto-confirm free orders upon cart validation

Orders are normally confirmed when the payment transaction
is processed, but there is no transaction for free orders.
This caused them to stay in draft until manually cancelled.

addons/website_sale/controllers/main.py

@@ -761,6 +761,10 @@ class website_sale(http.Controller):
             return request.redirect('/shop')
 
         if (not order.amount_total and not tx) or tx.state in ['pending', 'done']:
+            if (not order.amount_total and not tx):
+                # Orders are confirmed by payment transactions, but there is none for free orders,
+                # (e.g. free events), so confirm immediately
+                order.action_button_confirm()
             # send by email
             email_act = sale_order_obj.action_quotation_send(cr, SUPERUSER_ID, [order.id], context=request.context)
         elif tx and tx.state == 'cancel':