About client lifecycle

[wwhai]

Description

Should add an event interface which named OnConnected, Because that's only have OnConnect , But it seems only suit for todo something BEFORE connect，when we open Auth plugin，'OnConnected' maybe not trigger if auth failure。

Such bellow

type Events struct {
    OnProcessMessage // published message receieved before evaluation.
    OnMessage          // published message receieved.
    OnError                // server error.
    OnConnect           // client ready connect.
        OnConnected        // client connected.
    OnDisconnect       // client disconnected.
    OnSubscribe        // topic subscription created.
    OnUnsubscribe    // topic subscription removed.
}

[wind-c]

Authentication failure is also an error and can be detected by events#OnError.