WIP - Implement Capture the Notification Context in Designate Sink

This change captures the notification context in Designate Sink and passes it on to the notification handlers via the process_notification method.

blueprint sink-capture-notification-context

Change-Id: I8c3702d3ebec1b3d27b0302a10a9d219f62dec67
Merge "WIP - Implement Capture the Notification Context in Designate Sink"