Multiple improvements in authentication functionality

frontend/windows/flutter/generated_plugin_registrant.cc

@@ -6,6 +6,9 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <flutter_secure_storage_windows/flutter_secure_storage_windows_plugin.h>
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {
+  FlutterSecureStorageWindowsPluginRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("FlutterSecureStorageWindowsPlugin"));
 }