new user role customer that cannot see confidential issues

Description

I often have customers who would benefit from participating in certain discussions. Under current implementation if I allow customer in the gitlab as reporter, they can see all issues - but some of these issues are sensitive and don't need to be seen by them.

Currently we have confidential checkbox for issues that can be used to hide issue from guest users. But for customer project I usually have 100 internal issues, and only few that need to be visible to customer. That means I've to mark confidential on 100 issues! this seems like a lot of work. I think this ratio of confidential / visible issues is not specific to my case but a general rule of thumb in agencies.

Proposal

Implement a new role customer for whom all issues will be automatically confidential. And this role will see only issues created by them, or where they are mentioned @user.

Another way to go about this is to implement a global setting that would make all issues confidential by default like proposed here gitlab-ce#14551