PLT-3412 WebRTC Server side & System Console (#3706)

* WebRTC Server side

* WebRTC System Console

* Consistency on variable names

* Add turn and stun uri validation

model/websocket_message.go

@@ -25,6 +25,7 @@ const (
 	WEBSOCKET_EVENT_EPHEMERAL_MESSAGE  = "ephemeral_message"
 	WEBSOCKET_EVENT_STATUS_CHANGE      = "status_change"
 	WEBSOCKET_EVENT_HELLO              = "hello"
+	WEBSOCKET_EVENT_WEBRTC             = "webrtc"
 )
 
 type WebSocketMessage interface {