This page discusses the steps necessary to allow users to log in to your webserver. Of course, you can authenticate users to your server in any way you see fit. But Wt has some built-in user authentication resources available that make connecting to multiple user authentication services such as Google and Facebook, so it's possible to have an ID from one of those services provide authentication to your server.

Wt has a page for their authentication module which is a good starting point: https://www.webtoolkit.eu/wt/doc/tutorial/auth.html

I'll swing back around here and get some more notes on the subject.