Enhancement for Authorize.net - Duplicate window

-- HikaShop version -- : 2.6.3
-- Joomla version -- : 3.5.1

Hi, Nicolas & fellow HikaShop users -

We have a client who wanted the ability to configure the duplicate window for Authorize.net, so we made a small change to the code to add this feature.

By default, Authorize.net will treat a second attempt for the same amount as a duplicate transaction if it is within 2 minutes. This can easily happen if someone made a mistake with their address or other information that caused a declined transaction the first time, and they try again pretty quickly. It can be very frustrating for a customer to have the correct information declined as a duplicate.

The Authorize.net API allows you to set the decline window to something other than 2 minutes, so we have added a configuration field called "Duplicate Window". If you leave it blank, Authorize.net will use the standard 2 minute cutoff. Or you can set it to another timeframe by entering a number of seconds apart a transaction needs to be before it is not treated as a duplicate and declined by Authorize.net.

Nicolas, would you be willing to update the HikaShop Authorize.net plugin with this so it can be part of the official source code in future updates?