commerce-8.x-2.8/modules/promotion/commerce_promotion.routing.yml

entity.commerce_promotion_coupon.collection:
  path: '/promotion/{commerce_promotion}/coupons'
  defaults:
    _entity_list: 'commerce_promotion_coupon'
    _title: 'Coupons'
  options:
    _admin_route: TRUE
    parameters:
      commerce_promotion:
        type: 'entity:commerce_promotion'
  requirements:
    _entity_access: 'commerce_promotion.update'

entity.commerce_promotion_coupon.generate_form:
  path: '/promotion/{commerce_promotion}/coupons/generate'
  defaults:
    _form: '\Drupal\commerce_promotion\Form\CouponGenerateForm'
    _title: 'Generate coupons'
  options:
    _admin_route: TRUE
    parameters:
      commerce_promotion:
        type: 'entity:commerce_promotion'
  requirements:
    _permission: 'bulk generate commerce_promotion_coupon'