Rupay
    
    onEvent()
onEvent()
Method to subscribe for event changes. Subscribing to the events will enable the
            integration code to listen for state changes during the payment flows.
            The data argument of the callback will provide the ThreeDS method that was used to initiate the
            payment.
Usage
Rupay.onEvent(event, callback)
Example
Rupay.onEvent("EVENT_BEFORE_INITIATE_AUTHENTICATION", function (data) {
    //The data argument of the callback will provide the Rupay method that was used to initiate the payment
});
  
Arguments
        event
        
        Enumeration
        REQUIRED
    Event to subscribe to. See supported events list below.
EVENT_BEFORE_INITIATE_AUTHENTICATION
            EVENT_AFTER_INITIATE_AUTHENTICATION
            EVENT_BEFORE_AUTHENTICATE_PAYER
            EVENT_AFTER_AUTHENTICATE_PAYER
        
        callback
        
        Function
        REQUIRED
    The callback function
Return Value
None