Adding embedded PuSH server

app/workers/pubsubhubbub/delivery_worker.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class Pubsubhubbub::DeliveryWorker
+  include Sidekiq::Worker
+  include RoutingHelper
+
+  def perform(subscription_id, payload)
+    subscription = Subscription.find(subscription_id)
+    headers      = {}
+
+    headers['User-Agent']      = 'Mastodon/PubSubHubbub'
+    headers['Link']            = LinkHeader.new([[api_push_url, [%w(rel hub)]], [account_url(subscription.account, format: :atom), [%w(rel self)]]]).to_s
+    headers['X-Hub-Signature'] = signature(subscription.secret, payload) unless subscription.secret.blank?
+
+    response = HTTP.timeout(:per_operation, write: 50, connect: 20, read: 50)
+                   .headers(headers)
+                   .post(subscription.callback_url, body: payload)
+
+    raise "Delivery failed for #{subscription.callback_url}: HTTP #{response.code}" unless response.code > 199 && response.code < 300
+  end
+
+  private
+
+  def signature(secret, payload)
+    hmac = OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha1'), secret, payload)
+    "sha1=#{hmac}"
+  end
+end