Hide eMail addresses from participant suggestions (data protection)

Is your feature request related to a problem? Please describe.

In our organization, we have external contractors who we share a Nextcloud with. It is vital from a data protection perspective that those people only see each other under pseudonyms (nicknames, e.g. "FirstL") and no further personal information is visible to the others.

Problem: we can not use the calendar in its current form as no matter where we try to reduce eMail address visibility (or prohibit auto-completion in the "File Sharing" settings), we either get no suggested results at all or suggestions of user names with an eMail address in the next line:

Describe the solution you'd like

It would be great if users would be suggested as participants without showing their eMail address in the frontend! This kind of behavior works fine in "Deck", for example, and as far as I can tell anywhere you can mention users with "@"

The app still needs access to the eMail address of course, but in our case the majority of users does not need to see this at all and even administrators (who could legally be allowed to see the full information) are fine with only seeing names.

Describe alternatives you've considered

• Disable user profiles by default: no impact on eMail as it is required for certain functions

• completely disable Allow username autocompletion in share dialog and allow access to the system address book under "File Sharing" settings: only allows calendar invitations to be sent if entire eMail address is typed in by hand - too tedious to actually use

  • enabling Allow autocompletion when entering the full name or email address (ignoring missing phonebook match and being in the same group) is not really a solution as the name is visible in several places, so anyone could look up the eMail address via that name

Additional context

using Managed Nextcloud by IONOS

Start by reproducing the calendar participant suggestions described in the issue and compare their behavior with user mentions in Deck. Trace the frontend path that renders suggested participants and verify that suggestions show pseudonyms without email addresses while calendar invitations still work.