List characters

curl --request GET \
  --url https://platform.higgsfield.ai/v1/custom-references/list \
  --header 'hf-api-key: <hf-api-key>' \
  --header 'hf-secret: <hf-secret>'

{
  "total": 123,
  "page": 123,
  "page_size": 123,
  "total_pages": 123,
  "items": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "name": "<string>",
      "status": "not_ready",
      "thumbnail_url": "<string>",
      "created_at": "2023-11-07T05:31:56Z",
      "in_progress_at": "2023-11-07T05:31:56Z"
    }
  ]
}