const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({returnUrl: '<string>'})
};

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

{
  "authUrl": "<string>",
  "state": "<string>",
  "connectionId": "3c90c3cc-0d44-4b50-8888-8dd25736052a"
}