ActivityPub migration procedure (#4617)

* ActivityPub migration procedure

Once one account is detected as going from OStatus to ActivityPub,
invalidate WebFinger cache for other accounts from the same domain

* Unsubscribe from PuSH updates once we receive an ActivityPub payload

* Re-subscribe to PuSH unless already unsubscribed, regardless of protocol

app/workers/activitypub/post_upgrade_worker.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class ActivityPub::PostUpgradeWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'pull'
+
+  def perform(domain)
+    Account.where(domain: domain)
+           .where(protocol: :ostatus)
+           .where.not(last_webfingered_at: nil)
+           .in_batches
+           .update_all(last_webfingered_at: nil)
+  end
+end

app/workers/pubsubhubbub/unsubscribe_worker.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class Pubsubhubbub::UnsubscribeWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'push', retry: false, unique: :until_executed, dead: false
+
+  def perform(account_id)
+    account = Account.find(account_id)
+    logger.debug "PuSH unsubscribing from #{account.acct}"
+    ::UnsubscribeService.new.call(account)
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end

app/workers/scheduler/subscriptions_scheduler.rb

@@ -14,6 +14,6 @@ class Scheduler::SubscriptionsScheduler
   private
 
   def expiring_accounts
-    Account.where(protocol: :ostatus).expiring(1.day.from_now).partitioned
+    Account.expiring(1.day.from_now).partitioned
   end
 end