WebSocket must heartbeat

[tylerlong]

There is idleTimeout, by default it's 30 minutes. If in 30 minutes there is no traffic, the connection will time out:

{
    "errorCode": "WSG-902",
    "message": "Idle timeout expired"
  }

WebSocket ping frame doesn't count as traffic, so you cannot rely on WebSocket library's auto-ping feature.

It's not a problem for apps with lots of traffic. But for app with not so much traffic, the notification will stop working after 30 minutes.

Refer to the implementation in C# https://github.com/ringcentral/RingCentral.Net/blob/master/RingCentral.Net.WebSocket/WebSocketExtension.cs#L90-L101

[tylerlong]

I have fixed the issue for the Ruby SDK ringcentral/ringcentral-ruby@d07b09d...master

I am going to update the Python SDK.