Using DMF while creating Payment journal settle the Invoice with out posting

Using DMF creating Payment journal and mark the settle lines :

We need to extend CustomerPaymentJournalLineEntity - Data entity.

[ExtensionOf(tableStr(CustomerPaymentJournalLineEntity))]
Final class CustomerPaymentJournalLineEntity_CIT_Extension
{
    [PostHandlerFor(tableStr(CustomerPaymentJournalLineEntity), tableMethodStr(CustomerPaymentJournalLineEntity, mapEntityToDataSource))]
    public static void CustomerPaymentJournalLineEntity_Post_mapEntityToDataSource(XppPrePostArgs args)
    {
        CustTable   custtable;
        CustomerPaymentJournalLineEntity    customerPaymentJournalLineEntity = args.getThis() as CustomerPaymentJournalLineEntity;
        custtable   =   CustTable::find(customerPaymentJournalLineEntity.AccountDisplayValue);
        DataEntityDataSourceRuntimeContext dataSourceCtx    = args.getArg(identifierStr(_dataSourceCtx));
        switch (dataSourceCtx.name())
        {
            case dataEntityDataSourceStr(CustomerPaymentJournalLineEntity, LedgerJournalTrans):
                LedgerJournalTrans ledgerJournalTrans = dataSourceCtx.getBuffer();
                ledgerJournalTrans.initFromCustTable(custtable);
                /*if(!ledgerJournalTrans.MarkedInvoice)
                {
                    ledgerJournalTrans.CITErrorLog  =   NoYes::Yes; // if any error occurs while importing record from file a  field added to ledgerjournaltrans to notify it.
                }*/
                if ( LedgerJournalTrans.MarkedInvoice)
                {
                    if(!CustTrans::findFromInvoice(ledgerJournalTrans.MarkedInvoice).RecId)
                    {
                        ledgerJournalTrans.CITErrorLog  =   NoYes::Yes;
                    }
                }
                break;
        }

    }

    [DataEventHandler(tableStr(CustomerPaymentJournalLineEntity), DataEventType::PersistedEntity)]
    public static void CustomerPaymentJournalLineEntity_onPersistedEntity(Common _sender, DataEventArgs _eventArgs)
    {
        CustomerPaymentJournalLineEntity customerPaymentJournalLineEntity = _sender;
        LedgerJournalTrans      ledgerJournalTrans;
                     
        while select ledgerJournalTrans where customerPaymentJournalLineEntity.JournalBatchNumber == ledgerJournalTrans.JournalNum
            && customerPaymentJournalLineEntity.LineNumber == ledgerJournalTrans.LineNum
        {
            CustomerPaymentJournalLineEntity::insertLinesForLineLevelSettlement(ledgerJournalTrans,customerPaymentJournalLineEntity.CITDiscountAmount);
        }
    }

    private static void insertLinesForLineLevelSettlement(LedgerJournalTrans _ledgerJournalTrans, Amount _cashDisc)
    {
        CustTransOpen               custTransOpen;
        custTrans                   custTrans;
        CustVendOpenTransManager    manager;
        CustTransCashDisc           custTransCashDisc;

        Select custTransOpen where custTransOpen.accountNum == _ledgerJournalTrans.accountDisplay()
            Join custTrans where custTrans.Invoice == _ledgerJournalTrans.MarkedInvoice && custTrans.RecId == custTransOpen.RefrecId;
        If (custTransOpen)
        {
            if (_cashDisc)
            {
                custTransCashDisc.CashDiscAmount = _cashDisc;
                custTransCashDisc.CashDiscdate = systemdateget();
                custTransCashDisc.RefRecId = custTransOpen.RecId;
                custTransCashDisc.RefTableId = custTransOpen.TableId;
                custTransCashDisc.insert();
            }
            /*
            manager = CustVendOpenTransManager::construct(_ledgerJournalTrans);
            manager.updateSettleAmount(custTransOpen,_ledgerJournalTrans.AmountCurCredit);
            manager.updateTransMarked(custTransOpen,true);
            */
            SpecTrans specTrans;

            specTrans.SpecCompany = _ledgerJournalTrans.DataAreaId;
            specTrans.SpecRecId = _ledgerJournalTrans.RecId;
            specTrans.SpecTableId = _ledgerJournalTrans.TableId;
            specTrans.RefCompany = custTransOpen.DataAreaId;
            specTrans.RefRecId = custTransOpen.RecId;
            specTrans.RefTableId = custTransOpen.TableId;
            specTrans.code = _ledgerJournalTrans.CurrencyCode;
            specTrans.Balance01 = _ledgerJournalTrans.AmountCurCredit;
            specTrans.Payment = NoYes::No;
            specTrans.SelectedDateUsedToCalcCashDisc = today();
            specTrans.insert();

            ttsBegin;

            _ledgerJournalTrans.selectForUpdate(true);
            _ledgerJournalTrans.SettleVoucher    = SettlementType::SelectedTransact;
            _ledgerJournalTrans.update();

            ttsCommit;
        }
    }

}

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To Address discount while importing File:

Extend CustomerPaymentJournalLineEntity and add CITDiscountAmount.

If you want any of the fields to get populated from file values we need to add these fields if not exists
Ex: Document Number