Proposal: Restrict viewing certain (security) issues

[Oreolek]

Can we have a security filter? Gitlab has a checkbox that makes some issues visible only to "team members with at least Reporter access."

This is relevant to even the issue form itself because Github suggests sending a email instead of opening a public issue if it's a security concern. Gitea can be better than Github in that way.

[kolaente]

There is #3217 on that topic as well

[lunny]

@kolaente Oh, yes. This is a duplicated one.