tx_hash. The endpoint verifies the token contract and destination, records the withdraw request, converts the crypto amount to fiat, and triggers an Avada payout to the provided phone number.callback_url to receive asynchronous status updates as Unipesa progresses the payout.curl --location --request POST '/partners/transactions/withdraw-fiat' \
--header 'Content-Type: application/json' \
--data-raw '{
"from_currency": "USDC",
"to_currency": "KES",
"phone_number": "string",
"tx_hash": "string",
"callback_url": "string"
}'null