[Feature] Option to limit which users non-admins can see (share/invite dialogs)

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature On a shared instance, every non-admin user can see all other users of the server (name + email). The full user list shows up in every dialog where you pick another user: • "Add user" / "Invite to album" • Inviting someone to a people cluster group (Settings > Sharing) • "Add partner" (Settings > Sharing > Partners) Scenario: Friends A, B and C use my instance. A wants to share an album with B. A also sees C in the suggestions, although A should not know that C uses this server at all. Album sharing between users should keep working – users just shouldn't see everyone on the server. For a small self-hosted instance shared between people who don't necessarily know each other, this leaks personal data (names, email addresses, the fact that someone uses the server). W…