websocketConnectAsync
Asynchronously creates a class@WebsocketConnection to communicate with a remote server.
All necessary WebSocket-related headers will be added to @msg, and it will then be sent and asynchronously processed normally (including handling of redirection and HTTP authentication).
If the server returns "101 Switching Protocols", then @msg's status code and response headers will be updated, and then the WebSocket handshake will be completed. On success, method@Session.websocket_connect_finish will return a new class@WebsocketConnection. On failure it will return a #GError.
If the server returns a status other than "101 Switching Protocols", then
Parameters
#SoupMessage indicating the WebSocket server to connect to
origin of the connection
a null-terminated array of protocols supported
the I/O priority of the request
a #GCancellable
the callback to invoke