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

config/locales/en.yml

@@ -198,11 +198,13 @@ en:
         change_email_user: "%{name} changed the e-mail address of user %{target}"
         confirm_user: "%{name} confirmed e-mail address of user %{target}"
         create_account_warning: "%{name} sent a warning to %{target}"
+        create_announcement: "%{name} created new announcement %{target}"
         create_custom_emoji: "%{name} uploaded new emoji %{target}"
         create_domain_allow: "%{name} whitelisted domain %{target}"
         create_domain_block: "%{name} blocked domain %{target}"
         create_email_domain_block: "%{name} blacklisted e-mail domain %{target}"
         demote_user: "%{name} demoted user %{target}"
+        destroy_announcement: "%{name} deleted announcement %{target}"
         destroy_custom_emoji: "%{name} destroyed emoji %{target}"
         destroy_domain_allow: "%{name} removed domain %{target} from whitelist"
         destroy_domain_block: "%{name} unblocked domain %{target}"
@@ -224,10 +226,22 @@ en:
         unassigned_report: "%{name} unassigned report %{target}"
         unsilence_account: "%{name} unsilenced %{target}'s account"
         unsuspend_account: "%{name} unsuspended %{target}'s account"
+        update_announcement: "%{name} updated announcement %{target}"
         update_custom_emoji: "%{name} updated emoji %{target}"
         update_status: "%{name} updated status by %{target}"
       deleted_status: "(deleted status)"
       title: Audit log
+    announcements:
+      edit:
+        title: Edit announcement
+      empty: No announcements found.
+      live: Live
+      new:
+        create: Create announcement
+        title: New announcement
+      published: Published
+      time_range: Time range
+      title: Announcements
     custom_emojis:
       assign_category: Assign category
       by_domain: Domain
@@ -657,6 +671,9 @@ en:
     hint_html: "<strong>Tip:</strong> We won't ask you for your password again for the next hour."
     invalid_password: Invalid password
     prompt: Confirm password to continue
+  date:
+    formats:
+      default: "%b %d, %Y"
   datetime:
     distance_in_words:
       about_x_hours: "%{count}h"
@@ -758,6 +775,8 @@ en:
     all: All
     changes_saved_msg: Changes successfully saved!
     copy: Copy
+    delete: Delete
+    edit: Edit
     no_batch_actions_available: No batch actions available on this page
     order_by: Order by
     save_changes: Save changes
@@ -930,6 +949,9 @@ en:
     other: Other
     posting_defaults: Posting defaults
     public_timelines: Public timelines
+  reactions:
+    errors:
+      unrecognized_emoji: is not a recognized emoji
   relationships:
     activity: Account activity
     dormant: Dormant