title: Retrieve Keycloak user data using received access token
body: <p>I am developing a WildFly-Backend (in Java) that accepts HTTP requests (from a custom Frontend) that are signed with the user's Keycloak bearer access token through the "Authorization" HTTP header.</p>
  
  <p>The Backend connection itself is already secured with the Keycloak adapter for WildFly, but internally, I want to check who the user is (user groups, name, etc.) and return verying responses.</p>
  
  <p>I figured that it would be possible to just send this data from the Frontend, but then people could easily fake the request once they have an access token. Is there a way to retrieve things like user data while only having the access token?</p>