Feature: #89917 - Copy page access settings from parent

See forge#89917

Description

It is now possible to copy page access permissions from the parent page, while creating new pages. This is enabled using copyFromParent as value for one of the page TSconfig TCEMAIN.permissions.* sub keys.

There are casual scenarios where this can be useful to avoid additional backend administrator work:

On a top-level page, backend admins use the access module to set a page group owner and add TSconfig on this page to specify access details. A typical TSconfig is TCEMAIN.permissions.groupid to a group ID, plus TCEMAIN.permissions.group=31 to allow all members of this group to do "everything". To be sure, TCEMAIN.permissions.everybody=0 is set to deny access for non-members. Most often, a "page owner" base group is added, where all backend users are members of (directly or via subgroups). Access to single page trees are then done via page mount points in backend group "mount group records" that have this "page owner" group as subgroup. When a backend user being member of that "mount group" and thus having access to that page tree then creates new pages below this top-level page, the page owner is set to the creating user, and group ownership plus access details like "Can I modify?" are forced to the TSconfig settings of the top-level page.

With a base setup like that, administrators typically have to configure and set up page group ownership once per root site and are then sure that everything below "inherits" properly.

In more complex scenarios, different group owners are set for parts of a subpage tree. Administrators then want to make sure that new pages created below this differently restricted set of pages also inherit those changed group ownership settings when users create new pages. Until now, they had to change TCEMAIN.permissions.groupid and potentially TCEMAIN.permissions.group and TCEMAIN.permissions.everybody to achieve that and had to maintain TSconfig accordingly.

The new copyFromParent value can be leveraged to reduce administrator overhead to near-zero for access settings, especially when combined with defaultPageTSconfig. Let's say we have a TYPO3 instance with multiple sites. There is still a "page owner" group plus various other groups for backend user mount points to single sites. A basic site extension now sets this in an ext_tables.php file:

$GLOBALS['TYPO3_CONF_VARS']['BE']['defaultPageTSconfig'] .= '
    TCEMAIN.permissions.groupid = copyFromParent
    TCEMAIN.permissions.group = 31
    TCEMAIN.permissions.everybody = 0
';

This configures a default 'New pages are set to the owner of the parent page and members of this group can do "everything"'. When an administrator now creates a new site, it would set the "group" of that page using the access module to the "page owner" group once, and this will inherit to subpages automatically whenever a backend user creates a page. And all that without additional TSconfig settings. If an administrator later sets a different group owner for a subpage, new pages in there will inherit that owner instead, too.

From a Unix administrator's point of view, this setting is similar to the "group sticky bit" for directories - new directories get that group owner set by looking at the parent directory and inherit it to new subdirectories.

Example

TCEMAIN.permissions.userid = copyFromParent
TCEMAIN.permissions.groupid = copyFromParent
TCEMAIN.permissions.user = copyFromParent
TCEMAIN.permissions.group = copyFromParent
TCEMAIN.permissions.everybody = copyFromParent