@Override
    public String getPassword(String username) throws UserNotFoundException,
        UnsupportedOperationException
    {
        throw new UnsupportedOperationException();
    }
Implementation of auth provider interface for LDAP authentication service plug-in.
Only plaintext authentication is currently supported.<p>

Optionally, an authentication cache can be enabled. When enabled, a hashed version
of the user's password is cached for a variable length of time (2 hours by default).
This can decrease load on the directory and preserve some level of service even
when the directory becomes unavailable for a period of time.<ul>

 <li>{@code ldap.authCache.enabled} -- true to enable the auth cache.</li>
 <li>{@code ldap.authCache.size} -- size in bytes of the auth cache. If property is
     not set, the default value is 524288 (512 K).</li>
 <li>{@code ldap.authCache.maxLifetime} -- maximum amount of time a hashed password
     can be cached in milliseconds. If property is not set, the default value is
     7200000 (2 hours).</li>
</ul>

@author Matt Tucker
xmppserver/src/main/java/org/jivesoftware/openfire/ldap/LdapAuthProvider.java