How to get id of lead merged to user

The REST API has a method for merging contacts from lead to user. It works pretty simple:

```

curl -i -X POST https://api.intercom.io/contacts/merge \
  -H 'Authorization: Bearer <YOUR_TOKEN_HERE>' \
  -H 'Content-Type: application/json' \
  -H 'Intercom-Version: 2.10' \
  -d '{ "from": "LEAD_ID", "into": "USED_ID" }'

```

Also, lead can be merged to user in the Intercom app.

When lead is merged, our integration listen for webhook with topic `contact.merged`. This webhook has an information to what contact the lead was merged, but has a missing part from what lead:

```

{
  "type": "notification_event",
  "app_id": "abcdee",
  "data": {
    "type": "notification_event_data",
    "item": {
      "type": "contact",
      "id": "USER_ID",
      "workspace_id": "abcdee",
      "...": "..."
    }
  },
  "links": {},
  "topic": "contact.merged",
  "delivery_status": "pending",
  "delivery_attempts": 1,
  "delivered_at": 0,
  "first_sent_at": 1713533523,
  "created_at": 1713533523,
  "self": null
}

```

May you add lead ID to the webhook, so out server know what lead needs to merged on our side.

Thanks!