const options = {
  method: 'POST',
  headers: {'x-api-key': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    organization_id: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    data_owner_email: 'jsmith@example.com',
    facility_id: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    data_owner_user_id: '3c90c3cc-0d44-4b50-8888-8dd25736052a'
  })
};

fetch('https://api.dcycle.io/v1/custom-kpi-datasets/{dataset_id}/assignments', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "dataset_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "organization_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "data_owner_email": "<string>",
  "created_at": "2023-11-07T05:31:56Z",
  "facility_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "data_owner_user_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "updated_at": "2023-11-07T05:31:56Z"
}