AuthConfig object. This
 argument must not be null.</dd>
<dd><code>handler</code> - A CallbackHandler to be passed to the ClientAuthModules encapsulated by ClientAuthContext objects
 derived from the returned ClientAuthConfig. This argument may be null, in which case the implementation may assign a
 default handler to the configuration. The CallbackHandler assigned to the configuration must support the Callback
 objects required to be supported by the profile of this specification being followed by the mess