This merge request attempts to make the unbound package more user friendly by explicitly documenting the current behavior in a discoverable place (in line in the configuration file installed on the user's machine). The behavior is currently non-obvious as it requires checking the file's metadata rather than its contents, which is quite unusual for a configuration file in /etc.
The content of the documentation is derived from existing checked-in text, e.g. https://salsa.debian.org/dns-team/unbound/-/blob/master/debian/NEWS#L95-111