I have a need to integrate my Nation with an external system also hosted by us (on the same domain as our nation). The external system has user records and its own authentication. The external ids of these records are also present in our Nation.

What I really want is that when a user signs in to the external system they also sign in to our nation - i.e. I want a shared signon, but I cannot see any practical way of doing so.

Is there any avenue I can follow towards making this happen at all?