Better observers user permission

[jandrabek]

Current situation is that Observers can access any user details in workspace.

Problem
Any observer can find any user via @ and mention them in a comments.

Solution
Abillity to mention only user if they share same space or entity.

[Chr1sG]

Can we merge into this:

Hide People/User for non-admins

Currently: all users can see all other users, including their e-mail. This is a privacy issue. Idea: allow only admins to see all users. Use-Case: We work with external clients from different companies and they are not supposed to see each other’s e-mails The issue is mainly about: “People” menu item in the left menu - if that would be not visible to all users, that would be already a huge win (why do members even need that?) User entities that can be found through search and other means - s…

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