curl --request POST \
  --url https://www.carstoragesoftware.com/api/v1/billing/subscriptions/{id}/add-item \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "productId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "amountCents": 5000000,
  "priceId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "quantity": 50,
  "carId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "confirm": true,
  "previewToken": "<string>"
}
'

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    productId: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    amountCents: 5000000,
    priceId: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    quantity: 50,
    carId: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    confirm: true,
    previewToken: '<string>'
  })
};

fetch('https://www.carstoragesoftware.com/api/v1/billing/subscriptions/{id}/add-item', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://www.carstoragesoftware.com/api/v1/billing/subscriptions/{id}/add-item"

payload = {
    "productId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "amountCents": 5000000,
    "priceId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "quantity": 50,
    "carId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "confirm": True,
    "previewToken": "<string>"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

{
  "data": {
    "applied": true,
    "summary": "<string>",
    "action": "<string>",
    "previewToken": "<string>",
    "customerName": "<string>",
    "currency": "<string>",
    "interval": "<string>",
    "nextBillAt": "<string>",
    "before": {
      "lines": [
        {
          "lineId": "<string>",
          "productName": "<string>",
          "unitAmountCents": 123,
          "quantity": 123,
          "carLabel": "<string>",
          "change": "added"
        }
      ],
      "totalCents": 123
    },
    "after": {
      "lines": [
        {
          "lineId": "<string>",
          "productName": "<string>",
          "unitAmountCents": 123,
          "quantity": 123,
          "carLabel": "<string>",
          "change": "added"
        }
      ],
      "totalCents": 123
    },
    "newPriceWillBeCreated": true,
    "message": "<string>"
  }
}

{
  "error": "<string>",
  "code": "<string>",
  "details": null
}

{
  "error": "<string>",
  "code": "<string>",
  "details": null
}

{
  "error": "<string>",
  "code": "<string>",
  "details": null
}

{
  "error": "<string>",
  "code": "<string>",
  "details": null
}

{
  "error": "<string>",
  "code": "<string>",
  "details": null
}