Related to #2553

With #2887, a user who has access to modify roles will now have the ability to grant other user with permissions to the system indices. There is a potential of misuse here. If a rogue user, gets access to security index they can delete it causing no users to be able to access the cluster other than the super-admin who will have to create the index again.

What solution would you like?

Create a "denylist" setting which contains a list of system indices that are not permission-able to normal users.