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/services/post_status_service.rb

@@ -174,7 +174,7 @@ class PostStatusService < BaseService
   def poll_attributes
     return if @options[:poll].blank?
 
-    @options[:poll].merge(account: @account)
+    @options[:poll].merge(account: @account, voters_count: 0)
   end
 
   def scheduled_options