curl --request GET \
  --url https://toncenter.com/api/v3/nft/collections

{
  "address_book": {},
  "metadata": {},
  "nft_collections": [
    {
      "address": "<string>",
      "code_hash": "<string>",
      "collection_content": {},
      "data_hash": "<string>",
      "last_transaction_lt": "0",
      "next_item_index": "<string>",
      "owner_address": "<string>"
    }
  ]
}

{
  "code": 123,
  "error": "<string>"
}