curl --request GET \
  --url https://api.example.com/api/v2/external/orgs/{slug}/transactions/aggregate

{
  "aggregates": [
    {
      "group_by_value": "<string>",
      "count": 123,
      "total_amount": "<string>",
      "first_created_at": "2023-11-07T05:31:56Z",
      "last_created_at": "2023-11-07T05:31:56Z"
    }
  ]
}