docs: protected String getKeycloakUsername(final HttpServletRequest req, HttpServletResponse resp) {
          AtomicReference<String> username = new AtomicReference<>();
          Authenticator.authenticate(
              authConfiguration, req,
              subject -> {
                  username.set(AuthHelpers.getUsername(subject));
  
                  // Start httpSession
                  req.getSession(true);
              }
          );
          return username.get();
      }