Constructor.
The content of the web page's description tag.
Domain name of the looked up URL.
Message text if an exception was thrown during the lookup.
The HTTP response that was received when fetching the URL.
Web page title, or YouTube video title.
YouTube video author, if such a YouTube link.
A record of a URL lookup.
This is both used to aggregate information about the lookup, as well as to add hysteresis to lookups, so we don't look the same one up over and over if they were pasted over and over.