class type http_request_notification =object..end
 This object notifies the user that the request has fully arrived (including
 the body if accepted), and can now be responded. The environment is the
 same as in the request header notification, but the channels are now
 unlocked.
method req_state : engine_req_state`Received_request at the
 moment when this notification is delivered.method environment : extended_async_environmentmethod schedule_finish : unit -> unit