const form = new FormData();
form.append('file', '<string>');

const options = {method: 'POST'};

options.body = form;

fetch('https://api.dolfinai.co/bills', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
}