Retrieve or create user subscriptions

curl --request GET \
  --url https://sandbox.prezio.eu/api/users/subscriptions/ \
  --header 'Authorization: <api-key>'

{
  "count": 123,
  "next": "http://api.example.org/accounts/?page=4",
  "previous": "http://api.example.org/accounts/?page=2",
  "results": [
    [
      {
        "subscription_id": "sub_123456789",
        "plan_code": "sandbox",
        "status": "active",
        "created_at": "2025-06-17T20:48:00Z"
      }
    ]
  ]
}