handlers: permisison check for all pages + retrieve user-specific permissions for pages (if any)

handlers/handlerinvalidaction.h

@@ -5,10 +5,11 @@
 class HandlerInvalidAction : public Handler
 {
   public:
-	Response handle(const Request &r) override;
+	Response handleRequest(const Request &r) override;
 	~HandlerInvalidAction() override
 	{
 	}
+	bool canAccess(const Permissions &perms) override;
 	using Handler::Handler;
 };