/terra/market/v1beta1/swap
offer_coin defines the coin being offered (i.e. 1000000uluna).
ask_denom defines the denom of the coin to swap to.
curl -L \ --url 'https://lunc.nownodes.io//terra/market/v1beta1/swap'
{ "return_coin": { "denom": "text", "amount": "text" } }