Retrieves conversion rates

curl --request GET \
  --url https://staging-vouchers.ventogram.com/api/v1/currency/rates

{
  "success": true,
  "message": "<string>",
  "data": {
    "USDNGN": {
      "value": 490,
      "rateKey": "<string>",
      "description": "<string>"
    }
  }
}