Move admin/pubsubhubbub controller to admin/subscriptions (#3442)

app/controllers/admin/subscriptions_controller.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Admin
+  class SubscriptionsController < BaseController
+    def index
+      @subscriptions = ordered_subscriptions.page(requested_page)
+    end
+
+    private
+
+    def ordered_subscriptions
+      Subscription.order(id: :desc).includes(:account)
+    end
+
+    def requested_page
+      params[:page].to_i
+    end
+  end
+end