Get all categories for IPTC Media Topics

Example response

{
  "categories": [
    {
      "id": "bcd2d868-ed38-4382-b94a-622a30fc3215",
      "parent": "bcd2d868-ed38-4382-b94a-622a30fc3215",
      "children": [
        "bcd2d868-ed38-4382-b94a-622a30fc3215"
      ]
    }
  ]
}