Update doorkeeper to version 5.9.1 (#39132)

Gemfile.lock

@@ -210,7 +210,7 @@ GEM
       activerecord (>= 7.0, < 9.0)
     docile (1.4.1)
     domain_name (0.6.20240107)
-    doorkeeper (5.9.0)
+    doorkeeper (5.9.1)
       railties (>= 5)
     dotenv (3.2.0)
     drb (2.2.3)

config/application.rb

@@ -111,9 +111,6 @@ module Mastodon
     end
 
     config.to_prepare do
-      Doorkeeper::Application.include ApplicationExtension
-      Doorkeeper::AccessGrant.include AccessGrantExtension
-      Doorkeeper::AccessToken.include AccessTokenExtension
       Devise::FailureApp.include AbstractController::Callbacks
       Devise::FailureApp.include Localized
     end

config/initializers/doorkeeper.rb

@@ -179,3 +179,9 @@ Doorkeeper.configure do
   # WWW-Authenticate Realm (default "Doorkeeper").
   # realm "Doorkeeper"
 end
+
+Rails.application.reloader.to_prepare do
+  Doorkeeper.config.application_model.include ApplicationExtension
+  Doorkeeper.config.access_grant_model.include AccessGrantExtension
+  Doorkeeper.config.access_token_model.include AccessTokenExtension
+end