@Override
    protected boolean checkAuthentication() {
        return getSubject() == null || getSubject().getPrincipal() == null;
    }
Tag that renders the tag body if the current user <em>is not</em> known to the system, either because they
haven't logged in yet, or because they have no 'RememberMe' identity.

<p>The logically opposite tag of this one is the {@link UserTag}.  Please read that class's JavaDoc as it explains
more about the differences between Authenticated/Unauthenticated and User/Guest semantic differences.
support/jakarta-ee/src/main/java/org/apache/shiro/ee/faces/tags/GuestTag.java