This function is called from CRM_Contribute_Form_AdditionalPayment::postProcess, used for recording additional payments (partial payments as well as refunded payments).

It takes 3 arguments : 
 - <code>$contributionId</code> is the invoice contribution id (got created after processing participant payment)
 - <code>$trxnData</code> to take user provided input of transaction details.
 - <code>$paymentType</code> 'owed' for purpose of recording partial payments, 'refund' for purpose of recording refund payments