Show user display name on external share confirmation dialog

[fcharlaix-opendsi]

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Is your feature request related to a problem? Please describe.
When receiving a remote share from another server, the username show to the user is the Nextcloud login/ID.
This happens even with a trusted server or a known user (from contacts/lookup server).
This can be complicated to read when using user backend like LDAP, the login/ID is a UUID by default.

An example :

Describe the solution you'd like
When a remote share is received, Nextcloud should use a known display name (contacts, trusted servers, lookup server, etc…).
This aims to mimic the behavior of the share tab on the file informations with a remote share, this show the known display name.

The same share after being accepted in the said share tab :

Describe alternatives you've considered
Change the Nextcloud login name in the LDAP backend expert parameters.
This can create collision between user and need to recreate all accounts from scratch.