refactor(encryption): Migrate from hooks to events

[susnux]

Summary

Migrate code from hooks to typed events, also unify the user events as some had already a getUid method -> now all provide this convenient helper.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [ ] Tests (unit, integration, api and/or acceptance) are included
• [x] Screenshots before/after for front-end changes
• [ ] Documentation (manuals or wiki) has been updated or is not required
• [x] Backports requested where applicable (ex: critical bugfixes)

[susnux]

Not sure I like the getUid thing, especially since it uses a different casing than the method from IUser.

The IUser one is quite old, older than our naming guidelines that prefer Uid over UID (or Url over URL). But I am fine with removing it again, I just thought it would make sense to unify it as there are already events with getUid (exactly that casing).