Add streaming API updates for announcements being modified or deleted (#12963)

Change `all_day` to be a visual client-side cue only

Publish immediately if `scheduled_at` is in the past

Add `published_at` and `updated_at` to announcements JSON

app/workers/publish_scheduled_announcement_worker.rb

@@ -11,7 +11,7 @@ class PublishScheduledAnnouncementWorker
     payload = InlineRenderer.render(announcement, nil, :announcement)
     payload = Oj.dump(event: :announcement, payload: payload)
 
-    Account.joins(:user).where('users.current_sign_in_at > ?', User::ACTIVE_DURATION.ago).find_each do |account|
+    FeedManager.instance.with_active_accounts do |account|
       redis.publish("timeline:#{account.id}", payload) if redis.exists("subscribed:timeline:#{account.id}")
     end
   end