curl --request GET \
  --url https://api.paubox.net/v1/orca/{username}/subscription_lists \
  --header 'authorization: <api-key>'

{
  "data": [
    {
      "id": "<string>",
      "type": "subscription_list",
      "attributes": {
        "name": "<string>",
        "is_default": true,
        "subscriber_count": 123,
        "form_id": "<string>"
      }
    }
  ]
}