+ * ? filter => Filter expression to limit ldap search results.
+ * You can use this to *limit* the result set, based on specific
+ * requirements. The filter must be enclosed in parentheses, e.g.:
+ * '(objectclass=mailRecipient)'
+ * or '(&(objectclass=mailRecipient)(obectclass=myCustomClass))'
+ * The default value is empty.
+ *
+ * ? search_expression => Custom expression to expand ldap searches.
+ * This can help *expand* the result set, because of hits in more
+ * LDAP attributes. It must be a printf()-style string with either
+ * one placeholder '%s', or, if you want to repeat the expression
+ * many times, '%1$s'. The default value is:
+ * '(|(cn=*%1$s*)(mail=*%1$s*)(sn=*%1$s*))'
+ * that is, the search expression is search in the fields cn (common
+ * name), sn (surname) and mail.
+ *