Change notifications API to use a replica (#25874)

app/workers/merge_worker.rb

@@ -3,14 +3,15 @@
 class MergeWorker
   include Sidekiq::Worker
   include Redisable
+  include DatabaseHelper
 
   def perform(from_account_id, into_account_id)
-    ApplicationRecord.connected_to(role: :primary) do
+    with_primary do
       @from_account = Account.find(from_account_id)
       @into_account = Account.find(into_account_id)
     end
 
-    ApplicationRecord.connected_to(role: :read, prevent_writes: true) do
+    with_read_replica do
       FeedManager.instance.merge_into_home(@from_account, @into_account)
     end
   rescue ActiveRecord::RecordNotFound