from_currency, to_currency, amount, phone_number, wallet_address, and callback_url. The flow performs balance checks, applies partner fees, and triggers callbacks after completion.curl --location --request POST '/partners/transactions/topup-fiat' \
--header 'Content-Type: application/json' \
--data-raw '{
"from_currency": "KES",
"to_currency": "USDC",
"amount": 0,
"phone_number": "string",
"wallet_address": "string",
"callback_url": "string"
}'null