MDL-29527 - RSS: Add a description to the reset keys page

Thanks to Alexander Bias for the suggestion

lang/en/moodle.php

@@ -1391,6 +1391,7 @@
 $string['rsserror'] = 'Error reading RSS data';
 $string['rsserrorauth'] = 'Your RSS link does not contain a valid authentication token.';
 $string['rsserrorguest'] = 'This feed uses guest access to access the data, but guest does not have permission to read the data. Visit the original location that this feed comes from (URL) as a valid user and get a new RSS link from there.';
+$string['rsskeyshelp'] = 'To ensure security and privacy RSS feed URLs contain a special token that identifies the user they are for. This prevents other users from accessing areas of Moodle they shouldn\'t have access to via RSS feeds.</p><p>This token is automatically created the first time you access an area of Moodle that produces an RSS feed. If you feel that your RSS feed token has been compromised in some way you can request a new one by clicking the Reset link here. Please note that your present RSS feed URLs will then become invalid.';
 $string['rsstype'] = 'RSS feed for this activity';
 $string['saveandnext'] = 'Save and show next';
 $string['savedat'] = 'Saved at:';

rss/renderer.php

@@ -60,7 +60,7 @@ public function user_rss_token_box($token) {
         $return = $OUTPUT->heading(get_string('rss'), 3, 'main', true);
         $return .= $OUTPUT->box_start('generalbox webservicestokenui');
 
-        //$return .= get_string('keyshelp', 'webservice');
+        $return .= get_string('rsskeyshelp');
 
         $table = new html_table();
         $table->head  = array($strtoken, $stroperation);
@@ -82,4 +82,4 @@ public function user_rss_token_box($token) {
         $return .= $OUTPUT->box_end();
         return $return;
     }
-}
+}