Create a webhook

{
  "success": true,
  "message": "Webhook created successfully",
  "webhook": {
    "uuid": "a1b2c3d4-e5f6-4a7b-8c9d-0e1f2a3b4c5d",
    "name": "Production Webhook",
    "url": "https://example.com/webhook",
    "secret": "whsec_abc123def456...",
    "events": [
      "outbound.delivered",
      "outbound.bounced"
    ],
    "status": "enabled",
    "filter_users": null,
    "filter_domains": null,
    "created_at": 1736524800,
    "last_modified": 1736524800
  }
}

{
  "success": false,
  "error": "URL is required and must be a string"
}

{
  "success": false,
  "error": "User information not found"
}

{
  "success": false,
  "error": "Invalid filter_domains: example.com. You can only filter by domains that you own."
}

{
  "success": false,
  "error": "Failed to create webhook"
}