in a global scale setup, harmonize display name between local and remote users

[maximelehericy]

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

In a global scale setup, the display name differs depending on whether a user is located on the same instance or on a remote one.

I am login in with Alice account on instance A. Bob is also on instance A, and Charlie on instance C.
When Alice shares something with Bob, she sees "Bob" in the sharing dropdown.
When Alice shares something with Charlie, she sees "Charlie (remote)" in the sharing dropdown.

That is confusing users, when Global Scale is used to provide a unified Nextcloud experience for millions of users.

Describe the solution you'd like

When Global Scale is used to provide a unified Nextcloud experience for millions of users, we expect to have no difference in between users from local or "remote" instances.

In addition, with millions of users for sharing possibilities, the probability to have homonyms increases by a lot. To prevent that, we would like to have the email displayed, either in brackets, or in grey below the display name, as it is done for internal users:

Describe alternatives you've considered

Additional context