adjusted the ddi exporter to accommodate productionPlace having been made

multiple in PR #9254; would be great to put together a process for developers
who need to make changes to fields in metadata blocks that would help
them to know of all the places where changes like this need to be made.
(not the first time, when something breaks, in ddi export specifically, after
a field is made multiple). #3648

Author: landreev

src/main/java/edu/harvard/iq/dataverse/export/ddi/DdiExportUtil.java

@@ -1006,8 +1006,13 @@ private static void writeProducersElement(XMLStreamWriter xmlw, DatasetVersionDT
                 }
             }
         }
-        writeFullElement(xmlw, "prodDate", dto2Primitive(version, DatasetFieldConstant.productionDate));    
-        writeFullElement(xmlw, "prodPlac", dto2Primitive(version, DatasetFieldConstant.productionPlace));
+        writeFullElement(xmlw, "prodDate", dto2Primitive(version, DatasetFieldConstant.productionDate));
+        // productionPlace was made multiple as of 5.14:
+        // (a quick backward compatibility check was added to dto2PrimitiveList(),
+        // see the method for details)
+        for (String productionPlace : dto2PrimitiveList(version, DatasetFieldConstant.productionPlace)) {
+            writeFullElement(xmlw, "prodPlac", productionPlace);
+        }
         writeSoftwareElement(xmlw, version);
 
         writeGrantElement(xmlw, version);
@@ -1557,7 +1562,15 @@ private static List<String> dto2PrimitiveList(DatasetVersionDTO datasetVersionDT
             MetadataBlockDTO value = entry.getValue();
             for (FieldDTO fieldDTO : value.getFields()) {
                 if (datasetFieldTypeName.equals(fieldDTO.getTypeName())) {
-                    return fieldDTO.getMultiplePrimitive();
+                    // This hack is here to make sure the export does not blow 
+                    // up on an instance that upgraded to a Dataverse version
+                    // where a certain primitive has been made multiple, but has
+                    // not yet update the block. 
+                    if (fieldDTO.getMultiple()) {
+                        return fieldDTO.getMultiplePrimitive();
+                    } else {
+                        return Arrays.asList(fieldDTO.getSinglePrimitive());
+                    }
                 }
             }
         }