Hardening and security guidance - add information about strong directory permissions

Very often administrators want to know how the directory permissions of Nextcloud should be set best. I searched the Nextcloud documentation for information about it, but couldn't find a chapter covering it. The Hardening and security guidance doesn't cover this point either.

Nevertheless I had in mind that I read a chapter in the past, about how strong directory permissions should be set best. I searched the internet and found something in a Nextcloud pull request but its not mentioned or linked anywhere anymore.

Interestingly an older ownCloud documentation contained that information. A newer version of that documentation describes at least the installation wizard script.

I don't know why this information has been removed from the documentation but would like to get it added to it again.