switch to getTenderReferencedDocument analogue to getContractReferencedDocument, added DatedReference class and setters/getters for Invoice

library/src/main/java/org/mustangproject/DatedReference.java

@@ -0,0 +1,46 @@
+package org.mustangproject;
+
+import org.mustangproject.ZUGFeRD.IDatedReference;
+
+import java.beans.BeanProperty;
+import java.util.Date;
+
+public class DatedReference implements IDatedReference {
+
+	protected String ID;
+	protected Date opDate;
+
+	public DatedReference setDate(Date opDate) {
+		this.opDate = opDate;
+		return this;
+	}
+
+	public DatedReference setID(String ID) {
+		this.ID = ID;
+		return this;
+	}
+
+	public DatedReference() {
+
+	}
+
+	public DatedReference(String ID) {
+		setID(ID);
+	}
+
+	public DatedReference(String ID, Date theDate) {
+		setID(ID);
+		setDate(theDate);
+	}
+
+
+	@Override
+	public String getID() {
+		return ID;
+	}
+
+	@Override
+	public Date getDate() {
+		return opDate;
+	}
+}

library/src/main/java/org/mustangproject/Invoice.java

@@ -54,6 +54,7 @@ public class Invoice implements IExportableTransaction {
 	protected BigDecimal totalPrepaidAmount = null;
 	protected Date detailedDeliveryDateStart = null;
 	protected Date detailedDeliveryPeriodEnd = null;
+	protected IDatedReference tenderReference = null;
 
 	protected ArrayList<IZUGFeRDAllowanceCharge> Allowances = new ArrayList<>(),
 		Charges = new ArrayList<>(), LogisticsServiceCharges = new ArrayList<>();
@@ -144,6 +145,34 @@ public class Invoice implements IExportableTransaction {
 		return number;
 	}
 
+
+
+	@Override
+	/***
+	 * BT-17
+	 */
+	public IDatedReference getTenderReferencedDocument() {
+		return tenderReference;
+	}
+
+
+	/***
+	 * BT-17
+	 * @param dr
+	 * @return
+	 */
+	public Invoice setTenderReferencedDocument(DatedReference dr) {
+		tenderReference=dr;
+		return this;
+	}
+	
+	public Invoice setTenderReferencedDocument(String ID) {
+		DatedReference dr=new DatedReference(ID);
+		setTenderReferencedDocument(dr);
+		return this;
+	}
+
+
 	public Invoice setNumber(String number) {
 		this.number = number;
 		return this;

library/src/main/java/org/mustangproject/ZUGFeRD/IExportableTransaction.java

@@ -219,7 +219,7 @@ public interface IExportableTransaction {
 	 *
 	 * @return mandatory ID, optional Date
 	 */
-	default IDatedReference getTenderReference() {
+	default IDatedReference getTenderReferencedDocument() {
 		return null;
 	}
 

library/src/test/java/org/mustangproject/ZUGFeRD/ZF2EdgeTest.java

@@ -145,7 +145,7 @@ public class ZF2EdgeTest extends MustangReaderTestCase {
 	}
 
 	@Override
-	public IDatedReference getTenderReference() {
+	public IDatedReference getTenderReferencedDocument() {
 		return new IDatedReference() {
 			@Override
 			public String getID() {
@@ -159,6 +159,7 @@ public class ZF2EdgeTest extends MustangReaderTestCase {
 				} catch (ParseException e) {
 					// wont happen, I promise :-)
 				}
+				return null; // wont happen either
 			}
 		};
 	}

library/src/test/java/org/mustangproject/ZUGFeRD/ZF2PushTest.java

@@ -596,6 +596,7 @@ public class ZF2PushTest extends TestCase {
 			try {
 				SchemedID gtin = new SchemedID("0160", "2001015001325");
 				SchemedID gln = new SchemedID("0088", "4304171000002");
+				DatedReference dr=new DatedReference("90-kl-98798-C", sdf.parse("2025-10-12"));
 				ze.setTransaction(new Invoice().setCurrency("CHF").addNote("document level 1/2").addNote("document level 2/2").setDueDate(new Date()).setIssueDate(new Date()).setDeliveryDate(new Date()).setPaymentReference("Verwendungszweck").setDocumentName("Rechnung")
 					.setSellerOrderReferencedDocumentID("9384").setBuyerOrderReferencedDocumentID("28934")
 					.setDetailedDeliveryPeriod(new SimpleDateFormat("yyyyMMdd").parse(occurrenceFrom), new SimpleDateFormat("yyyyMMdd").parse(occurrenceTo))
@@ -608,6 +609,7 @@ public class ZF2PushTest extends TestCase {
 					.addCharge(new Charge(new BigDecimal(0.5)).setReason("quick delivery charge").setTaxPercent(new BigDecimal(16)))
 					.addAllowance(new Allowance(new BigDecimal(0.2)).setReason("discount").setTaxPercent(new BigDecimal(16)))
 					.addCashDiscount(new CashDiscount(new BigDecimal(2), 14))
+					.setTenderReferencedDocument(dr)
 					.setDeliveryDate(sdf.parse("2020-11-02")).setNumber(number).setVATDueDateTypeCode(EventTimeCodeTypeConstants.PAYMENT_DATE)
 					.setInvoiceReferencedDocumentID("abc123").addInvoiceReferencedDocument(new ReferencedDocument("abcd1234"))
 				);