Triggers after admin approves the join request.

<?php
function my_component_init(){
		ossn_register_callback('group', 'approve:request', 'my_component_cb');
}
function my_component_cb($callback, $type, array $params){
		//$params['user_guid'] and $params['group_guid'] 
}
ossn_register_callback('ossn', 'init', 'my_component_init');