Ensure destruction of OAuth Applications notifies streaming

Due to doorkeeper using a dependent: delete_all relationship, the destroy of an OAuth Application bypassed the existing AccessTokenExtension callbacks for announcing destructing of access tokens.

app/lib/application_extension.rb

@@ -4,14 +4,29 @@ module ApplicationExtension
   extend ActiveSupport::Concern
 
   included do
+    include Redisable
+
     has_many :created_users, class_name: 'User', foreign_key: 'created_by_application_id', inverse_of: :created_by_application
 
     validates :name, length: { maximum: 60 }
     validates :website, url: true, length: { maximum: 2_000 }, if: :website?
     validates :redirect_uri, length: { maximum: 2_000 }
+
+    # The relationship used between Applications and AccessTokens is using
+    # dependent: delete_all, which means the ActiveRecord callback in
+    # AccessTokenExtension is not run, so instead we manually announce to
+    # streaming that these tokens are being deleted.
+    before_destroy :push_to_streaming_api, prepend: true
   end
 
   def confirmation_redirect_uri
     redirect_uri.lines.first.strip
   end
+
+  def push_to_streaming_api
+    # TODO: #28793 Combine into a single topic
+    access_tokens.in_batches.each do |token|
+      redis.publish("timeline:access_token:#{token.id}", Oj.dump(event: :kill))
+    end
+  end
 end