tasks #7336: Add table in db to handle users who unsubscribe to artifact notification.

Change-Id: Id0a4be532703d7deb7c40f444ab789a2cf1ad4e4
Merge commit 'refs/changes/80/2880/3' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  tasks #7336: Add table in db to handle users who unsubscribe to artifact notification.
This is Tuleap 7.3.99.51

Change-Id: I6b54f617cd7d7fc25c9c571feccef8cf7571582e