e authentication server <strong>CANNOT</strong> invalidate credentials after they are issued, then simply return <code>true</code>
for this method. If the authentication server <strong>CAN</strong> invalidate credentials due to security breaches, then
read on.</p>

<p>When an authentication server can invalidate credentials, it means that you may have a non-expired credential
that appears to be valid, but will be rejected by the authentication server when used. Generally when this
happens, a number of reque