Listen before authentication

Steam sends some messages to the client immediately on authentication.

If you need to listen to those messages, you can create a connection without logging in yet by using UnAuthenticatedConnection::connect.

Unauthenticated connections cannot be used to send messages, but you can use it to start listening on messages before authenticating.

Once you're started listening for all the messages you require, you can convert an UnAuthenticatedConnection into a authenticated Connection by using anonymous, anonymous_server or login.