Storage Cleanup

[nadar]

We need a way to find outdated files, images to cleanup the storage system. Especially images which can be regenerated by its file could be cleaned up in order save space and shrink the db table size.

There are old parts which seems not to work, https://github.com/luyadev/luya-module-admin/blob/master/src/commands/StorageController.php