#61 Fix location of prettyprint.xsl + Add some Unit Tests

- Fix after v6.2 Merge: Move prettyprint.xsl to the correct folder (otherwise prettyPrintXML method doesn't work and FundingReferences are not send to Datacite)
- Add some Unit Tests for DataCiteMetadataUtil

src/test/java/edu/harvard/iq/dataverse/pidproviders/doi/DataCiteMetadataUtilTest.java

@@ -0,0 +1,78 @@
+package edu.harvard.iq.dataverse.pidproviders.doi;
+
+import org.junit.jupiter.api.Test;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.xml.sax.SAXException;
+
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+import java.io.IOException;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+class DataCiteMetadataUtilTest {
+
+    @Test
+     void testParseXml() throws ParserConfigurationException, IOException, SAXException {
+        String testXML = this.createTestXML();
+
+        org.w3c.dom.Document document = XmlMetadataTemplate.DataCiteMetadataUtil.parseXml(testXML);
+
+        assertNotNull(document);
+        assertEquals("UTF-8", document.getXmlEncoding());
+        assertEquals("root", document.getDocumentElement().getNodeName());
+        assertEquals("firstElement", document.getDocumentElement().getChildNodes().item(1).getNodeName());
+    }
+
+    @Test
+    void testAppendElementToDocument() throws ParserConfigurationException{
+        org.w3c.dom.Document document = this.createTestDocument();
+        String parentTagName = "secondElement";
+        String tageName = "firstChildOfSecondElement";
+        String textContent = "text of firstChildOfSecondElement";
+
+        XmlMetadataTemplate.DataCiteMetadataUtil.appendElementToDocument(document, parentTagName, tageName, textContent);
+
+        assertEquals(1, document.getElementsByTagName(parentTagName).getLength());
+        Node addedChildNode = document.getElementsByTagName(parentTagName).item(0).getFirstChild();
+        assertEquals(tageName, addedChildNode.getNodeName());
+        assertEquals(textContent, addedChildNode.getTextContent());
+    }
+
+    @Test
+    void testPrettyPrintXML() throws Exception {
+        org.w3c.dom.Document document = this.createTestDocument();
+
+        String xmlMetadata = XmlMetadataTemplate.DataCiteMetadataUtil.prettyPrintXML(document, 4);
+
+        String secondLine = xmlMetadata.split(System.lineSeparator())[1];
+        assertEquals("<root>", secondLine);
+        String thirdLine = xmlMetadata.split(System.lineSeparator())[2];
+        assertEquals("    ", thirdLine.substring(0,4));
+    }
+
+    private String createTestXML(){
+        return """
+                <?xml version="1.0" encoding="UTF-8" standalone="no"?>
+                <root>
+                    <firstElement>Text of a TestNode.</firstElement>
+                    <secondElement/>
+                </root>
+                """;
+    }
+
+    private org.w3c.dom.Document createTestDocument() throws ParserConfigurationException {
+        org.w3c.dom.Document document = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
+        Element rootElement = document.createElement("root");
+        document.appendChild(rootElement);
+        Element firstElement = document.createElement("firstElement");
+        rootElement.appendChild(firstElement);
+        firstElement.appendChild(document.createTextNode("Text of a TestNode."));
+        Element secondElement = document.createElement("secondElement");
+        rootElement.appendChild(secondElement);
+
+        return document;
+    }
+
+}