controller: notification when last control point reached
Submitted by Uli Franke
Provide a way to get a callback, message or similar when a control automation via control source or similar reached its final value, i.e. when automation finished.
This is useful to detect when automation finished and subsequent actions can be taken or to chain automation properly.
For instance fading out before pipeline pause to avoid clicks: start fade out automation, wait for callback, pause pipeline.