Add announcements (#12662)

* Add announcements

Fix #11006

* Add reactions to announcements

* Add admin UI for announcements

* Add unit tests

* Fix issues

- Add `with_dismissed` param to announcements API
- Fix end date not being formatted when time range is given
- Fix announcement delete causing reactions to send streaming updates
- Fix announcements container growing too wide and mascot too small
- Fix `all_day` being settable when no time range is given
- Change text "Update" to "Announcement"

* Fix scheduler unpublishing announcements before they are due

* Fix filter params not being passed to announcements filter

app/workers/scheduler/scheduled_statuses_scheduler.rb

@@ -6,14 +6,38 @@ class Scheduler::ScheduledStatusesScheduler
   sidekiq_options unique: :until_executed, retry: 0
 
   def perform
+    publish_scheduled_statuses!
+    publish_scheduled_announcements!
+    unpublish_expired_announcements!
+  end
+
+  private
+
+  def publish_scheduled_statuses!
     due_statuses.find_each do |scheduled_status|
       PublishScheduledStatusWorker.perform_at(scheduled_status.scheduled_at, scheduled_status.id)
     end
   end
 
-  private
-
   def due_statuses
     ScheduledStatus.where('scheduled_at <= ?', Time.now.utc + PostStatusService::MIN_SCHEDULE_OFFSET)
   end
+
+  def publish_scheduled_announcements!
+    due_announcements.find_each do |announcement|
+      PublishScheduledAnnouncementWorker.perform_at(announcement.scheduled_at, announcement.id)
+    end
+  end
+
+  def due_announcements
+    Announcement.unpublished.where('scheduled_at IS NOT NULL AND scheduled_at <= ?', Time.now.utc + PostStatusService::MIN_SCHEDULE_OFFSET)
+  end
+
+  def unpublish_expired_announcements!
+    expired_announcements.in_batches.update_all(published: false)
+  end
+
+  def expired_announcements
+    Announcement.published.where('ends_at IS NOT NULL AND ends_at <= ?', Time.now.utc)
+  end
 end