Idempotency-Key: <string arbitrario, máx 255 caracteres>

# Primera llamada
curl -X POST 'https://tools.vivla.com/api/public/events/ingest' \
  -H 'x-api-key: <NOTIFICATIONS_API_KEY>' \
  -H 'Idempotency-Key: booking_abc123_created' \
  -H 'Content-Type: application/json' \
  -d '{
    "event_type": "booking.created",
    "aggregate_id": "booking_abc123",
    "aggregate_type": "booking",
    "payload": { ... }
  }'

# Respuesta:
# HTTP/1.1 202 Accepted
# X-Request-ID: req_a1b2c3
# {
#   "object": "event",
#   "id": "<uuid>",
#   "type": "booking.created",
#   "status": "pending",
#   "created_at": "..."
# }

# Reintento (mismo key, mismo body) — aceptable
# HTTP/1.1 200 OK
# {
#   "object": "event",
#   "id": "<mismo uuid>",
#   "type": "booking.created",
#   "status": "idempotent",
#   "created_at": "..."
# }

# Misma key con body distinto — error
# HTTP/1.1 409 Conflict
# { "error": { "code": "idempotency_key_in_use", ... } }

async function ingestEvent(event: Event): Promise<EventResource> {
  const key = `${event.aggregateId}:${event.eventType}:${event.timestamp}`
  // Determinístico: si reintento por timeout, recalculo la misma key
  for (let attempt = 0; attempt < 3; attempt++) {
    try {
      const res = await fetch('.../public/events/ingest', {
        method: 'POST',
        headers: {
          'x-api-key': API_KEY,
          'Idempotency-Key': key,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify(event),
      })
      if (res.ok) return await res.json()
      if (res.status === 429) {
        const retryAfter = Number(res.headers.get('Retry-After') ?? '5')
        await sleep(retryAfter * 1000)
        continue
      }
      // 4xx no-rate-limit: error del cliente, no reintentar
      throw await res.json()
    } catch (err) {
      // Network error: reintentar con la MISMA key (que es lo bueno de idempotency)
      if (attempt === 2) throw err
      await sleep(2 ** attempt * 1000)
    }
  }
  throw new Error('unreachable')
}