Move lux usage in luxletterlink to signal

[georgringer]

The LuxletterLink used ext lux. Even though there is a guard clause to check if the extension is installed, the code should be moved to the signal right above.

protected function luxIdentification(Link $link): void
    {
        $identification = true;
        $this->signalDispatch(__CLASS__, __FUNCTION__, [&$identification, $link]);
        if (ExtensionUtility::isLuxAvailable('7.0.0') && $identification === true) {
            CookieUtility::setCookie('luxletterlinkhash', $link->getHash());
        }
    }

[einpraegsam]

Yes, would be a bit cleaner. I let this ticket open as a reminder for me.