curl --request GET \
  --url https://api.contazen.ro/v1/invoices/{id}/payment-estimate \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "data": {
    "status": "unpaid",
    "estimated_at": "2023-12-25",
    "due_at": "2023-12-25",
    "days_from_now": 123,
    "days_overdue": 123,
    "confidence": "low",
    "basis": {
      "source": "client_history",
      "sample_size": 123,
      "avg_days_to_pay": 123,
      "client_on_time_pct": 123
    }
  },
  "meta": {
    "version": "v1",
    "request_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "response_time": "23.45ms"
  }
}