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

fetch('http://localhost:4005/v1/arc/projects/:id/members/:userId', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "success": true,
  "data": {
    "id": "<string>",
    "projectId": "<string>",
    "userId": "<string>",
    "role": "admin",
    "createdAt": "2023-11-07T05:31:56Z"
  },
  "meta": {
    "requestId": "<string>",
    "timestamp": "<string>"
  }
}