@billyudi We are working on a update to the upgrade guide which will discuss how to map the new theme files and changes.

You can follow along with it here:

https://github.com/FusionAuth/fusionauth-site/pull/2166

I get your larger question though, which is, if I customize my theme, and then I upgrade from 1.45 to 1.46 and 1.46 introduces a new themed page, what does that new themed page look like?

Have you tried testing this out?

You would have to add a hook in your IdP to make an API call to delete the user in FusionAuth. However, because the SoR will no longer have this user, the use will not be able to log in via FusionAuth either unless their password is reset.

We have discussed adding support for SCIM which may provide some of these types of features assuming other IdPs also support this standard. This is on the roadmap: https://github.com/FusionAuth/fusionauth-issues/issues/106