When PuSH subscribe attempts are exhausted, unsubscribe (#4422)

app/workers/pubsubhubbub/subscribe_worker.rb

@@ -3,7 +3,7 @@
 class Pubsubhubbub::SubscribeWorker
   include Sidekiq::Worker
 
-  sidekiq_options queue: 'push', retry: 10, unique: :until_executed
+  sidekiq_options queue: 'push', retry: 10, unique: :until_executed, dead: false
 
   sidekiq_retry_in do |count|
     case count
@@ -18,6 +18,12 @@ class Pubsubhubbub::SubscribeWorker
     end
   end
 
+  sidekiq_retries_exhausted do |msg, _e|
+    account = Account.find(msg['args'].first)
+    logger.error "PuSH subscription attempts for #{account.acct} exhausted. Unsubscribing"
+    ::UnsubscribeService.new.call(account)
+  end
+
   def perform(account_id)
     account = Account.find(account_id)
     logger.debug "PuSH re-subscribing to #{account.acct}"