service cas.gateway_subscriber in CAS 2.x

class: Drupal\cas\Subscriber\CasGatewayAuthSubscriber
arguments:
  - '@current_route_match'
  - '@config.factory'
  - '@current_user'
  - '@plugin.manager.condition'
  - '@cas.helper'
  - '@cas.redirector'
tags:
  - { name: event_subscriber }