Cancel a previously created merchant transaction.

This endpoint allows for the creation of cancellation transactions that reverse the financial impact of original sale transactions. Cancellation transactions maintain negative amounts of all financial values (amount, MDR, fees) and reference the original transaction via origin_merchant_transaction_id.

When the original transaction was split, the cancellation status is automatically set to WAITING_SPLIT, otherwise it follows the default status (SCHEDULED).

This endpoint generates a Merchant transaction created event.