Permit password security for some spaces

It is known that anybody who is in the confluence-administrator group can access any restricted spaces. Since we have an improvement request to remove the confluence-administrator's privileges(to access any space), a customer suggested in a ticket to restrict spaces using passwords, in that way, confluence administrators won't be able to access sensitive content as we have some tickets and Atlassian Answers regarding this kind of issue.

Steps to replicate:

1. Create a new Space.
2. Create a test group
3. Restrict the space only for the test group.
4. Access the space using the admin user