Comment 4 for bug 1443284

Reviewed: https://reviews.mahara.org/8251
Committed: https://git.mahara.org/mahara/mahara/commit/17131a35785e8cb0654a61d03eeb407557b0ad38
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 17131a35785e8cb0654a61d03eeb407557b0ad38
Author: Robert Lyon <email address hidden>
Date: Wed Nov 1 14:26:02 2017 +1300

Bug 1443284: Allow an unsubscribe link for watchlist emails

This patch:
- adds an 'unsubscribetoken' column to usr_watchlist_view table
(if we want to unsubscribe other messages we'd need to add an
'unsubscribetoken' to the relevant table)
- records the token when one watches the view
- sends email with unsubscribe link with message type and token to
avoid exposing any user data
- link goes to unsubscribe.php page and either unsubscribes user or
gives generic warning

Currently only working for watchlist notifications being sent via
email/email digest

Change-Id: I823249108f521faaefe3435f03b84ddf73e2d360
Signed-off-by: Robert Lyon <email address hidden>