The identifier that should trigger this service. Or return null
if you want to filter all 404 queries. For example "/admin".
You can specify a service that should filter multiple identifiers by
separating them with a ':' character. For example: if you want to
identify a user before multiple services, return "/update:/query" here
and set the index to 0 on the identity service and set index to 1 on the
update and query filters. Then you use the following code to redirect to
the login page for example:
event.daemon().chain(event, "/login").filter(event);
throw event; // stop the chain
or
event.reply().header("Location", "/login");
event.reply().code("302 Found");
throw event; // stop the chain