Board Game Arena

Is there any way to know who is a spectator of my game? Any way to send notification to the spectators other than notifyAllPlayers()?

I have a scenario where I want to notify some players & all spectators. Is there way to do this, or do I need to send to all with parameter like 'ignore' => array( $player1, $player2 ) to handle on client side?

If this is confidential information you cannot send it to spectators, why would you exclude some players from that?
If it just repeat of information it should be fine (and I don't know of API to to send it to spectators)