Add voters count support (#11917)

* Add voters count to polls

* Add ActivityPub serialization and parsing of voters count

* Add support for voters count in WebUI

* Move incrementation of voters count out of redis lock

* Reword “voters” to “people”

app/serializers/activitypub/note_serializer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class ActivityPub::NoteSerializer < ActivityPub::Serializer
-  context_extensions :atom_uri, :conversation, :sensitive
+  context_extensions :atom_uri, :conversation, :sensitive, :voters_count
 
   attributes :id, :type, :summary,
              :in_reply_to, :published, :url,
@@ -23,6 +23,8 @@ class ActivityPub::NoteSerializer < ActivityPub::Serializer
   attribute :end_time, if: :poll_and_expires?
   attribute :closed, if: :poll_and_expired?
 
+  attribute :voters_count, if: :poll_and_voters_count?
+
   def id
     ActivityPub::TagManager.instance.uri_for(object)
   end
@@ -141,6 +143,10 @@ class ActivityPub::NoteSerializer < ActivityPub::Serializer
 
   alias end_time closed
 
+  def voters_count
+    object.preloadable_poll.voters_count
+  end
+
   def poll_and_expires?
     object.preloadable_poll&.expires_at&.present?
   end
@@ -149,6 +155,10 @@ class ActivityPub::NoteSerializer < ActivityPub::Serializer
     object.preloadable_poll&.expired?
   end
 
+  def poll_and_voters_count?
+    object.preloadable_poll&.voters_count
+  end
+
   class MediaAttachmentSerializer < ActivityPub::Serializer
     context_extensions :blurhash, :focal_point