an></dt>
<dd><code>provider</code> - The AuthConfigurationProvider whose registration identifiers are to be returned. This argument may be
 null, in which case it indicates that the IDs of all active registrations within the factory are to be returned.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>An array of String values where each value identifies a provider registration at the factory. This method
 never returns null; it returns an empty array when there are no registrations at the factory