The syntax ?<...> seems to be only supported from PCRE 7.0 on. For
backwards-compability ?P<...> is used.

Tooltip contains 'Unable to determine date'. Fixes #6395

$userId is now a mandatory parameter for searchByTags.

Also fixed some places in the code where the argument was missing (Node
API and View)

The file:// protocol does not work with curl when an open_basedir is set.

This fixes https://github.com/owncloud/core/issues/12016

use more flexible return type

check array with !empty instead of count

This adds a "backend" type filter to the index REST route which is a pre-requisite for https://github.com/owncloud/core/issues/12620

For example when calling `index.php/settings/users/users?offset=0&limit=10&gid=&pattern=&backend=OC_User_Database` only users within the backend `OC_User_Database` would be shown. (requires sending a CSRF token as well)

Depends upon https://github.com/owncloud/core/pull/12711

Make DateTimeFormatter a service and adjust tests that have been inaccurate

Fix #12227