const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    tenant_id: '01935-tttt-tttt-tttt-tttttttttttt',
    event_name: 'order.shipped',
    data: {order_id: '4567'},
    idempotency_key: 'evt-4567-shipped'
  })
};

fetch('{protocol}://{host}/api/v1/engine/events', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "event_id": "01935-eeee-…",
  "subscriptions_matched": 2,
  "execution_ids": [
    "01935-aaaa-…",
    "01935-bbbb-…"
  ]
}