Anonymize auth.users and user_profile data instead of deleting it.

[vvalchev]

Currently, it is allowed to delete users and their public profiles. That however is not always great.

What I've seen in Confluence as an example if a user has created a page, and then this user is gone from the company, the page is still there, e.g. it keeps the same user as the owner. The only thing that's changed is that you will see that the owner is a deleted user.

The benefit of that is, when you delete a user, you don't have to change all relations to it, which might be a very slow operation. And yet, according to the GDPR we must be able to delete user-sensitive data. With data anonymization, we keep the user ID and all references intact, we just replace the sensitive data.