View source for Forum update/Discussion subscription

== Per-discussion subscription model (MDL-1626) ==
=== Issue description ===
The current subscription model for forums is for a user to be subscribed to an entire forum, or unsubscribed from that entire forum. On busy forums, a user may find the quantity of e-mail generated to be too high. As a result, they may (and do) either unsubscribe, or filter out the e-mails that they receive. This has a negative effect on the pedagogical value of the forum as a whole.
== Proposed Solution ==
One of the most-requested changes to the forum, with over 150 votes, is for a per-discussion subscription option. This proposed solutions gives users the option to:
opt into a discussion for a forum which they do not receive notifications for; and to
opt out of a particular discussion for a forum where they receive notifications.
=== Subscription type implications ===
This has different implications for the different forum subscription options available in Moodle. These options are:
Forced subscription - all users are subscribed to the forum;
Automatic subscription - all users are subscribed to the forum, but any can choose to unsubscribe;
Optional subscription - no user is subscribed, but all users can choose to subscribe; and
Subscription disabled - it is not possible to subscribe at all.
==== Forced subscription and Subscription disabled ====
For forums where either Forced subscription and Subscription disabled are selected, there will be no change. A force subscribed forum will continue to ensure that all users always receive subscription content. A forum with subscription disabled will continue to prevent delivery of any kind.
==== Automatic subscription ====
For a forum which is automatically subscribed, users will continue to be subscribed automatically.
'''''Change''': Users will have the option of unsubscribing from an individual discussion.''
==== Optional subscription ====
For a forum with an optional subscription model, users will continue to be able to subscribe to the forum as a whole, but will not be subscribed automatically.
'''''Change''': Users will have the option of subscribing to an individual discussion.''
=== Module-level subscription type changes ===
==== Switching from any option to Forced subscription mode ====
User preference data is left unmodified
==== Switching from any option to Subscription disabled mode ====
User preference data is left unmodified
==== From Optional subscription to Automatic subscription ====
For users who had not previously opted in, we currently just subscribe all users.
'''''Potential change''': The teacher is asked whether unsubscribed users should now be subscribed to the forum, or just new users to the forum.''

For users who had previously opted in, we currently preserve the existing setting.
''No change proposed.''

When a user has set per-discussion opt-in or opt-out preferences
''No change will be made on that user’s behalf when a their inclusion is changed at the module level.
The preferences are redundant but these are user preferences rather than tutor preferences and the tutor should not be able to modify them. If a user wishes to change their subscription back to the previous setting, they should be able to achieve their previous status quo.''

==== From Automatic subscription to Optional subscription ====

For users who had previously opted in, we currently just unsubscribe all users.
'''''Potential change''': The teacher is asked whether subscribed users should now be unsubscribed to the forum, or just new users to the forum.''

For users who had previously opted out of the forum as a whole, no change is made. There is no data to preserve.

When a user has set per-discussion opt-in or opt-out preferences
''No change will be made on that user’s behalf when a their inclusion is changed at the module level.
The preferences are redundant but these are user preferences rather than tutor preferences and the tutor should not be able to modify them. If a user wishes to change their subscription back to the previous setting, they should be able to achieve their previous status quo.''

=== User-level subscription changes ===
When a user in an automatic or optional forum changes their subscription, what happens to per-discussion options?
''All per-discussion preferences for that forum are removed.''

== Tasks ==
See MDL-1626. A working prototype of this functionality has been implemented during the planning phase which implements the above design decisions