This method should be overridden if required to obtain any additional
roles for the given user (on top of those obtained from the standard
search implemented by this class).
LDAP server name(s) separated by spaces, optionally with TCP port number, like "ldap.acme.org"
or "ldap.acme.org:389" and/or with protcol, like "ldap://ldap.acme.org".