post https://{environment}.masspay.io/{VERSION}/payin/
This POST endpoint initiates a pay-in transaction from a user to your account.
Use this endpoint to collect funds from users — for example, deposits, payments, or wallet top-ups.
Provide the payer's user_token in the URL path, and include in the request body the source of funds (source_token), deposit destination (destination_token), and the currency of the pay-in (source_currency_code).
The response returns complete details of the pay-in transaction, including status, amounts, and references.