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

1 files changed, 19 insertions, 0 deletions

diff --git a/app/policies/announcement_policy.rb b/app/policies/announcement_policy.rb
new file mode 100644
index 000000000..0a4e4575c
--- /dev/null
+++ b/app/policies/announcement_policy.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class AnnouncementPolicy < ApplicationPolicy
+  def index?
+    staff?
+  end
+
+  def create?
+    admin?
+  end
+
+  def update?
+    admin?
+  end
+
+  def destroy?
+    admin?
+  end
+end