Handle unauthorized

[sprite2005]

I only allow authorized users to connect ActionCable, if the user is unauthorized I call reject_unauthorized_connection from Rails.

This sends a response

{
"type": "disconnect",
"reason": "unauthorized",
"reconnect": false
}

This package will crash on line 127 in action_cable.dart:

final channelId = parseChannelId(payload['identifier']);

Because there is no identifier as we are not yet connected to a channel and a channel disconnect callback wouldn't be appropriate anyways since it's disconnecting the client.

We need to check if reason is 'unauthorized' and then call either onConnectionLost or onCannotConnect. I think onCannotConnect would be most appropriate, perhaps even passing the reconnect: false so we know not to retry the connection.

Let me know if you want to make this change or if I should just fork.

[sprite2005]

Something as simple as this should work if you don't want to break current API, although it would be nice if we could pass retry, since I'm sure a lot of people have automatic connection retry handling on cannot connect.

      case 'disconnect':
        final identifier = payload['identifier'];
        if (identifier != null) {
          final channelId = parseChannelId(payload['identifier']);
          final onDisconnected = _onChannelDisconnectedCallbacks[channelId];
          if (onDisconnected != null) {
            onDisconnected();
          }
        } else {
          final reason = payload['reason'];
          if (reason != null && reason == 'unauthorized') {
            if (this.onCannotConnect != null) this.onCannotConnect!();
          }
        }
        break;