Authentication for an app through Auth SDK

We’d like to be able to have an Angular front end pass a username/password to a WebApi backend and have the WebApi do the auth through the SDK, however this only gives us a session token and not an access token/user claims. How do we get these once the session token has been obtained?

I just realised about this also, the auth-js does not provide any way to get the access token, only the session token.

Investigating this further it seems recommended that we should do this at the backend hence that bit is missing from the auth-js library