curl --request POST \
  --url https://api.hyperline.co/v1/subscriptions/{id}/simulate-updates \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "application_schedule": "immediately",
  "apply_at": "2024-12-20T16:04:11Z",
  "payment_schedule": "immediately",
  "calculation_method": "pro_rata",
  "updates": [
    {
      "type": "add_product",
      "payload": {
        "product_id": "<string>",
        "product_name": "<string>",
        "product_description": "<string>",
        "count": 1,
        "billing_interval_period": "days",
        "billing_interval_count": 123,
        "start_or_end": "start",
        "display_interval_dates_in_description": true,
        "type": "fee",
        "prices": [
          {
            "type": "fee",
            "amount": 123
          }
        ]
      }
    }
  ]
}'

{
  "amount": 123
}