MDL-66481 mod_forum: Move timed discussion indicator

* Move it under the discussion column.
* Change it to look like a label
* Plus limit the group name to 15 characters
* Plus some accessibility fixes:
  - Add labels to column headings.
  - Set discussion name as a row heading.

mod/forum/amd/src/discussion_list.js

@@ -119,6 +119,11 @@ define([
 
             e.preventDefault();
         });
+
+        root.on('click', Selectors.discussion.timedLabel, function(e) {
+            // Prevent clicking on the timed discussion label from causing the page to jump.
+            e.preventDefault();
+        });
     };
 
     return {

mod/forum/amd/src/selectors.js

@@ -69,6 +69,7 @@ define([], function() {
             item: '[data-region="discussion-list-item"]',
             lockedLabel: "[data-region='locked-label']",
             subscribedLabel: "[data-region='subscribed-label']",
+            timedLabel: "[data-region='timed-label']",
         },
     };
 });

mod/forum/lang/en/forum.php

@@ -191,10 +191,12 @@
 $string['discussthistopic'] = 'Discuss this topic';
 $string['displayend'] = 'Display end';
 $string['displayend_help'] = 'This setting specifies whether a forum post should be hidden after a certain date. Note that administrators can always view forum posts.';
+$string['displayenddate'] = 'Display end: {$a}.';
 $string['displaymode'] = 'Display mode';
 $string['displayperiod'] = 'Display period';
 $string['displaystart'] = 'Display start';
 $string['displaystart_help'] = 'This setting specifies whether a forum post should be displayed from a certain date. Note that administrators can always view forum posts.';
+$string['displaystartdate'] = 'Display start: {$a}.';
 $string['displaywordcount'] = 'Display word count';
 $string['displaywordcount_help'] = 'This setting specifies whether the word count of each post should be displayed or not.';
 $string['duedate'] = 'Due date';
@@ -637,6 +639,8 @@
 $string['thisforumisthrottled'] = 'This forum has a limit to the number of forum postings you can make in a given time period - this is currently set at {$a->blockafter} posting(s) in {$a->blockperiod}';
 $string['thisforumisdue'] = 'The due date for posting to this forum was {$a}.';
 $string['thisforumhasduedate'] = 'The due date for posting to this forum is {$a}.';
+$string['timed'] = 'Timed';
+$string['timeddiscussion'] = 'Timed discussion';
 $string['timedhidden'] = 'Timed status: Hidden from students';
 $string['timedposts'] = 'Timed posts';
 $string['timedvisible'] = 'Timed status: Visible to all users';