I'm hosting my Saas on Fly.io and I've setup a custom domain (say, abcdef.com). I use Google OAuth, and when I log in, it directs to the fly.io domain (abcdef-client.fly.dev)instead of the custom domain (abcdef.com). When I setup the client variables WASP_WEB_CLIENT_URL and WASP_SERVER_URL to abcdef.com, when I log into google I get a 404 (page not found) error. When I set them to their fly.io URLs, it works fine, but the URL shows abcdef-client.fly.dev.
How do I remedy it so that it always goes to the custom domain??