We want to disable phpMyAdmin access to specific database users as most of our database connections happen in the cluster itself, with no external access needed.
The preferred way would have a boolean on the cluster API's `database-users` layer.
The attribute `phpmyadmin_firewall_groups_ids` has been added to database users.
It is a nullable list of firewall groups. When no firewall groups are allowed, i.e. an empty list, phpMyAdmin access is fully disabled.