onBuildOngoingCallNotification    
  open fun onBuildOngoingCallNotification(builder: NotificationCompat.Builder, callId: StreamCallId, callDisplayName: String? = null, isOutgoingCall: Boolean = false, remoteParticipantCount: Int = 0, payload: Map<String, Any?>): NotificationCompat.Builder
Intercept the notification builder and modify it before it is posted.
Parameters
builder
The notification builder.
callDisplayName  
The name of the caller to display in the notification.
isOutgoingCall  
True if the call is outgoing, false if it is an active call.
remoteParticipantCount  
Count of remote participant.