owncloud/core

Enhancement: expiration date for user and group shares

Shares with users and/or groups can now be given an expiration date.
If the default expiration date is enabled then the default expiration is 7 days
in the future. The default expiration date can be modified by the administrator.
The default expiration date can be enforced as the maximum expiration date of a
share. In that case the user can select a shorter expiration, but not longer.

The settings are disabled by default, preserving the existing behavior. They can
be enabled on the admin sharing settings page. They can be set independently for
user and group shares.

https://github.com/owncloud/core/pull/36573
https://github.com/owncloud/core/pull/36766
https://github.com/owncloud/core/pull/36847