Show more details in user search

[SamuelWei]

Is your feature request related to a problem? Please describe.
Users have complained that it is sometimes difficult to identify users in the user search for adding room members.
This is especially a problem when several users have the same first and last name. To uniquely identify the user, the email would be helpful.

Describe the solution you'd like
Show the firstname, lastname and email in the search. Maybe also add the user type (manual, ldap, shibboleth, etc.)

Describe alternatives you've considered
none

Additional context
none