Limit User Results When Adding Page Restrictions to Only Relevant Users

Problem Definition

Currently, when users are restricting a page on Space that is limited to specific groups, they are still seeing all users when searching for people on the Restrictions section:

This can be confusing as it will show users that do not have access to the Space, and may mislead people in thinking that they can add people that don't have the correct Space Permissions.

Suggested Solution

Have the Restrictions section on a page only return Users that already have access to the Space should it be locked down to specific groups.