curl --request POST \
  --url https://api.upwell.com/api/rest/bill_line_items \
  --header 'Content-Type: application/json' \
  --data '
{
  "input": {
    "billId": "<string>",
    "description": "<string>",
    "item": "<string>",
    "lineNumber": "<string>",
    "quantity": 123,
    "sourceSystem": "<string>",
    "sourceSystemId": "<string>",
    "totalAmount": 123,
    "unitPrice": 123
  }
}
'

{
  "createBillLineItem": {
    "billId": "<string>",
    "createdAt": "2023-11-07T05:31:56Z",
    "description": "<string>",
    "id": "<string>",
    "item": "<string>",
    "lineNumber": "<string>",
    "quantity": 123,
    "sourceSystem": "<string>",
    "sourceSystemId": "<string>",
    "totalAmount": 123,
    "unitPrice": 123,
    "updatedAt": "2023-11-07T05:31:56Z"
  }
}