FIX: Ensure do-not-disturb icon updates correctly (#28253)

`currentUser.do_not_disturb_until` is a string, so we need to parse it before comparing to the current timestamp

app/serializers/current_user_serializer.rb

@@ -12,6 +12,7 @@ class CurrentUserSerializer < BasicUserSerializer
              :read_first_notification?,
              :admin?,
              :notification_channel_position,
+             :do_not_disturb_channel_position,
              :moderator?,
              :staff?,
              :whisperer?,
@@ -320,4 +321,8 @@ class CurrentUserSerializer < BasicUserSerializer
   def use_glimmer_topic_list?
     scope.user.in_any_groups?(SiteSetting.experimental_glimmer_topic_list_groups_map)
   end
+
+  def do_not_disturb_channel_position
+    MessageBus.last_id("/do-not-disturb/#{object.id}")
+  end
 end