Code Improvement: Disable access to external entities in XML parsing.

* Update from `.newInstance()` to `.newDefaultInstance()` which should add the flags for critical security risks.

Author: MartinWheelerMT

service/src/main/java/uk/nhs/adaptors/gp2gp/common/service/XPathService.java

@@ -25,7 +25,7 @@
 @Component
 public class XPathService {
     public Document parseDocumentFromXml(String xml) throws SAXException {
-        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
+        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newDefaultInstance();
         InputSource inputSource;
         DocumentBuilder documentBuilder;
         try {

service/src/main/java/uk/nhs/adaptors/gp2gp/gpc/StructuredRecordMappingService.java

@@ -174,7 +174,7 @@ public String buildSkeletonEhrExtractXml(String realEhrExtract, String documentI
     }
 
     private static String toString(Document document) throws TransformerException {
-        TransformerFactory tf = TransformerFactory.newInstance();
+        TransformerFactory tf = TransformerFactory.newDefaultInstance();
         Transformer transformer = tf.newTransformer();
         StringWriter writer = new StringWriter();