external_user_id. Funds are moved from the member’s Safe to the pool wallet, then Unipesa is invoked to pay out fiat to the member’s phone. The optional callback URL lets partners receive completion or failure notices without polling.curl --location --request POST '/partners/transactions/withdraw-fiat/member' \
--header 'Content-Type: application/json' \
--data-raw '{
"from_currency": "USDC",
"to_currency": "KES",
"amount": 0,
"external_user_id": "string",
"callback_url": "string"
}'{
"from_currency": "USDC",
"to_currency": "KES",
"amount": 0,
"external_user_id": "string",
"id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
"status": "string",
"pool_tx_hash": "string",
"wallet_address": "string",
"phone_number": "string",
"created_at": "2019-08-24T14:15:22Z",
"updated_at": "2019-08-24T14:15:22Z"
}