Add result_count to Mastodon-Async-Refresh header when needed (#36239)

app/controllers/concerns/async_refreshes_concern.rb

@@ -6,6 +6,9 @@ module AsyncRefreshesConcern
   def add_async_refresh_header(async_refresh, retry_seconds: 3)
     return unless async_refresh.running?
 
-    response.headers['Mastodon-Async-Refresh'] = "id=\"#{async_refresh.id}\", retry=#{retry_seconds}"
+    value = "id=\"#{async_refresh.id}\", retry=#{retry_seconds}"
+    value += ", result_count=#{async_refresh.result_count}" unless async_refresh.result_count.nil?
+
+    response.headers['Mastodon-Async-Refresh'] = value
   end
 end