Creates a transaction and executes our payment screening and transaction monitoring processes. The response will indicate whether the transaction should be held or processed. Updates a transaction if a transaction with the same external_identifier, occurred_at, customer_external_identifier and details.type already exists but other data has changed. Supports updating existing transactions on the Synchronous Transaction Monitoring flow only; not supported for fast payment screening or async flows. This endpoint requires PAYMENT_SCREENING_BASE and/or TRANSACTION_MONITORING_BASE account permission depending on the configuration identifies supplied with the payload.