Credential saving to XML introduced to support pre-shared credentials

lib/TLS/include/Credentials.h

@@ -128,6 +128,19 @@ namespace eap
         /// \name XML credentials management
         /// @{
 
+        ///
+        /// Save credentials to XML document
+        ///
+        /// \param[in]  pDoc         XML document
+        /// \param[in]  pConfigRoot  Suggested root element for saving credentials
+        /// \param[out] ppEapError   Pointer to error descriptor in case of failure. Free using `module::free_error_memory()`.
+        ///
+        /// \returns
+        /// - \c ERROR_SUCCESS if succeeded
+        /// - error code otherwise
+        ///
+        virtual DWORD save(_In_ IXMLDOMDocument *pDoc, _In_ IXMLDOMNode *pConfigRoot, _Out_ EAP_ERROR **ppEapError) const;
+
         ///
         /// Load credentials from XML document
         ///