In a nutshell, this plugin allows you to share sessions between your application and NodeBB. You'll need to set a
special cookie with a common domain, containing a JSON Web Token with user data. If sufficient, this plugin will
handle the rest (user registration/login).
How is this related to SSO?
Single Sign-On allows a user to log into NodeBB through a third-party service. It is best (and most securely)
achieved via OAuth2 provider, although other alternatives exist. An example of a single sign-on plugin is
Single sign-on does not allow a session to become automatically created if a login is made to another site.
This is the one misconception that people hold when thinking about SSO and session sharing.
This session sharing plugin will allow NodeBB to automatically log in users (and optionally, log out users)
if the requisite shared cookie is found (more on that below).
You can use this plugin and single sign-on plugins together, but they won't be seamlessly integrated.
How does this work?
This plugin checks incoming requests for a shared cookie that is saved by your application when a user
logs in. This cookie contains in its value, a specially crafted signed token containing unique identifying
information for that user.
If the user can be found in NodeBB, that user will be logged in. If not, then a user is created, and that
unique indentifier is saved for future reference.