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/publish_announcement_reaction_worker.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class PublishAnnouncementReactionWorker
+  include Sidekiq::Worker
+  include Redisable
+
+  def perform(announcement_id, name)
+    announcement = Announcement.find(announcement_id)
+
+    reaction,  = announcement.announcement_reactions.where(name: name).group(:announcement_id, :name, :custom_emoji_id).select('name, custom_emoji_id, count(*) as count, false as me')
+    reaction ||= announcement.announcement_reactions.new(name: name)
+
+    payload = InlineRenderer.render(reaction, nil, :reaction).tap { |h| h[:announcement_id] = announcement_id }
+    payload = Oj.dump(event: :'announcement.reaction', payload: payload)
+
+    Account.joins(:user).where('users.current_sign_in_at > ?', User::ACTIVE_DURATION.ago).find_each do |account|
+      redis.publish("timeline:#{account.id}", payload) if redis.exists("subscribed:timeline:#{account.id}")
+    end
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end