Yes, I believe the way to do it with the free version is to use this: https://github.com/zmartzone/lua-resty-openidc

You'd have to be careful with custom code like this, though, because it's very easy to try to get the server to send a redirect but end up sending actual content that just has its HTTP status code changed to 301. The example seems to fail with 500 instead of redirecting, that's one way to do it.