Create X activity subscription

curl --request POST \
  --url https://api.x.com/2/activity/subscriptions \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "filter": {
    "keyword": "The President",
    "user_id": "2244994945"
  },
  "tag": "<string>",
  "webhook_id": "1146654567674912769"
}
'

{
  "data": {
    "subscription": {
      "created_at": "2023-11-07T05:31:56Z",
      "event_type": "<string>",
      "filter": {
        "keyword": "The President",
        "user_id": "2244994945"
      },
      "subscription_id": "1146654567674912769",
      "updated_at": "2023-11-07T05:31:56Z",
      "tag": "<string>",
      "webhook_id": "1146654567674912769"
    },
    "total_subscriptions_for_instance_id": 123
  },
  "errors": [
    {
      "title": "<string>",
      "type": "<string>",
      "detail": "<string>",
      "status": 123
    }
  ],
  "meta": {
    "total_subscriptions": 123
  }
}