Add warning for CORS issue

[PaulAsjes]

When using middleware auth mode and Next.js server actions, it's possible to trigger a CORS issue. The edge case manifests itself when:

1. User doesn't have a valid session (i.e. logged out in a separate tab)
2. User triggers a server action in the now stale page
3. CORS error surfaces in the browser console

The above happens because without a valid session and in middleware auth mode, the POST request to the server action is intercepted and a redirect to AuthKit is attempted, which triggers a CORS error.

The solution here is to wrap the server action call in a try/catch block so an error can displayed or the user redirected client side.

Also updates Next.js to its latest minor version.