add framework for post update pushes to pubsub

app/models/post.rb

@@ -1383,15 +1383,9 @@ class Post < ActiveRecord::Base
     end
 
     def notify_pubsub
-      return
       return unless Danbooru.config.google_api_project
 
-      pubsub = Google::Apis::PubsubV1::PubsubService.new
-      pubsub.authorization = Google::Auth.get_application_default([Google::Apis::PubsubV1::AUTH_PUBSUB])
-      topic = "projects/#{Danbooru.config.google_api_project}/topics/post_updates"
-      request = Google::Apis::PubsubV1::PublishRequest.new(messages: [])
-      request.messages << Google::Apis::PubsubV1::Message.new(data: id.to_s)
-      pubsub.publish_topic(topic, request)
+      PostUpdate.insert(id)
     end
   end