curl --request GET \
  --url https://api.courier.com/lists/{list_id}/subscriptions \
  --header 'Authorization: Bearer <token>'

{
  "paging": {
    "cursor": "<string>",
    "more": true
  },
  "items": [
    {
      "recipientId": "<string>",
      "created": "<string>",
      "preferences": {
        "categories": {},
        "notifications": {}
      }
    }
  ]
}