curl --request GET \
  --url http://localhost:3000/v1/reference/categories

{
  "categories": [
    {
      "id": "<string>",
      "name": "<string>",
      "level": 123,
      "parent_id": "<string>",
      "children": [
        "<unknown>"
      ]
    }
  ],
  "count": 123
}