curl --request GET \
  --url https://api.example.com/v1/knowledge-base/{document_id}/rag-index

{
  "indexes": [
    {
      "id": "<string>",
      "status": "created",
      "progress_percentage": 50,
      "document_model_index_usage": {
        "used_bytes": 1
      },
      "model": "gemini-embedding-001"
    }
  ]
}