An application can subscribe to one or more valid call events for an IMS subscriber.
When a call direction subscription filter is matched for an incoming or outgoing call,
the Telephony Application Server (Nokia TAS) suspends its call
and sends the matched event via POST to the specified destination URL (of 3rd Party Application Server).
The Nokia TAS waits for response to determine the call disposition treatment.
CalledNumber, Answer, NoAnswer, Busy, Disconnected, NotReachable
To mash up data from other sources to change the calling pattern/experience