add document code

src/main/java/org/mustangproject/ZUGFeRD/IZUGFeRDExportableTransaction.java

@@ -27,10 +27,21 @@ package org.mustangproject.ZUGFeRD;
  * */
 
 
+import org.mustangproject.ZUGFeRD.model.DocumentCodeTypeConstants;
+
 import java.util.Date;
 
 public interface IZUGFeRDExportableTransaction {
 
+	/**
+	 *
+	 *
+	 * @return Code of Document
+	 */
+	default String getDocumentCode() {
+		return DocumentCodeTypeConstants.INVOICE;
+	}
+
 	/**
 	 * Number, typically invoice number of the invoice
 	 *

src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDImporter.java

@@ -209,6 +209,13 @@ public class ZUGFeRDImporter {
 		return result;
 	}
 
+	/**
+	 * @return the document code
+	 */
+	public String getDocumentCode() {
+		return extractString("//HeaderExchangedDocument/TypeCode");
+	}
+
 	/**
 	 * @return the sender's bank's BLZ code
 	 */

src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDTransactionModelConverter.java

@@ -94,7 +94,7 @@ class ZUGFeRDTransactionModelConverter {
 		document.setIssueDateTime(issueDateTime);
 
 		DocumentCodeType documentCodeType = xmlFactory.createDocumentCodeType();
-		documentCodeType.setValue(DocumentCodeTypeConstants.INVOICE);
+		documentCodeType.setValue(trans.getDocumentCode());
 		document.setTypeCode(documentCodeType);
 
 		TextType name = xmlFactory.createTextType();