post https://earthnode-dev.vopay.com/api/v2/gcm/conversion
This endpoint is used to perform a conversion from one currency to another. You can either specify how much of the source currency that you wish to sell, or how much of the target currency you wish to buy (either the BuyAmount OR SellAmount must be specified).
If BuyAmount is specified then the SellAmount will be calculated based on the current exchange rate. If SellAmount is specified the BuyAmount will be calculated based on the current exchange rate.