Make SamlResponse more extensible

The query and queryAssertion methods are really useful when creating
extensions of SamlResponse that need to expose other information that
the plain java-saml library does not (like the response issue instant,
or any custom contents of the AuthnContext in the assertion auth
statement). Having these two methods private forces the extender to
reimplement them from scratch, probably by copy-and-paste, which is
clearly sub-optimal.

Author: mauromol

core/src/main/java/com/onelogin/saml2/authn/SamlResponse.java

@@ -1033,7 +1033,7 @@ public Exception getValidationException() {
 	 * @throws XPathExpressionException
 	 *
 	 */
-	private NodeList queryAssertion(String assertionXpath) throws XPathExpressionException {
+	protected NodeList queryAssertion(String assertionXpath) throws XPathExpressionException {
         final String assertionExpr = "/saml:Assertion";
         final String signatureExpr = "ds:Signature/ds:SignedInfo/ds:Reference";
 
@@ -1084,16 +1084,9 @@ private NodeList queryAssertion(String assertionXpath) throws XPathExpressionExc
      *
      * @return DOMNodeList The queried nodes
      */
-	private NodeList query(String nameQuery, Node context) throws XPathExpressionException {
-		Document doc;
-		if (encrypted) {
-			doc = decryptedDocument;
-		} else {
-        	doc = samlResponseDocument;
-		}
-
+	protected NodeList query(String nameQuery, Node context) throws XPathExpressionException {
 		// LOGGER.debug("Executing query " + nameQuery);
-		return Util.query(doc, nameQuery, context);
+		return Util.query(getSAMLResponseDocument(), nameQuery, context);
 	}
 
 	/**