public static UmbracoBackOfficeIdentity GetUmbracoBackOfficeIdentity(HttpContextBase http)
 {
     var ticket = http.GetUmbracoAuthTicket();
     if (ticket != null && !ticket.Expired && http.RenewUmbracoAuthTicket())
     {
         return new UmbracoBackOfficeIdentity(ticket);
     }
     return null;
 }