postoffice-1.0.x-dev/postoffice.routing.yml

postoffice.site_settings:
  path: '/admin/config/system/postoffice'
  defaults:
    _form: '\Drupal\postoffice\Form\SiteSettingsForm'
    _title: 'Postoffice settings'
  requirements:
    _permission: 'administer postoffice configuration'