Further refactor

app/controllers/api/v1/push/subscriptions_controller.rb

@@ -43,11 +43,11 @@ class Api::V1::Push::SubscriptionsController < Api::BaseController
   private
 
   def destroy_web_push_subscriptions!
-    Web::PushSubscription.where(access_token_id: doorkeeper_token.id).destroy_all
+    doorkeeper_token.web_push_subscriptions.destroy_all
   end
 
   def set_push_subscription
-    @push_subscription = Web::PushSubscription.find_by(access_token_id: doorkeeper_token.id)
+    @push_subscription = doorkeeper_token.web_push_subscriptions.first
   end
 
   def check_push_subscription

app/lib/access_token_extension.rb

@@ -6,6 +6,8 @@ module AccessTokenExtension
   included do
     include Redisable
 
+    has_many :web_push_subscriptions, class_name: 'Web::PushSubscription', inverse_of: :access_token
+
     after_commit :push_to_streaming_api
   end