Retrieves a list of custom collections.

Example response

{
  "custom_collection": [
    {
      "body_html": "<p>The best selling iPods ever</p>",
      "handle": "IPods",
      "id": 632910392,
      "image": {
        "alt": "iPods",
        "created_at": "2018-04-19T09:34:47-04:00",
        "height": 488,
        "src": "https://img.btdmp.com/collections/ipod.jpg",
        "width": 500
      },
      "metafields": [
        {
          "key": "description_tag",
          "namespace": "global",
          "value": "description_tag",
          "value_type": "string"
        }
      ],
      "published": true,
      "sort_order": "best-selling",
      "title": "IPods"
    }
  ]
}