Use a minimum age of items to remove

In order to keep deleted items for a while, the periodic task can now
use a duration to only remove items with a certain age. This can be
used to ensure that a deleted item stays at least X days before it
will be removed from the database.

Refs: #347

modules/store/src/main/resources/db/migration/mariadb/V1.25.2__add_trash_min_age.sql

@@ -0,0 +1,8 @@
+ALTER TABLE `empty_trash_setting`
+ADD COLUMN (`min_age` bigint);
+
+UPDATE `empty_trash_setting`
+SET `min_age` = 604800000;
+
+ALTER TABLE `empty_trash_setting`
+MODIFY `min_age` bigint NOT NULL;