Load Rails 6.1 framework defaults

This loads Rails 6.1 defaults but overrides some values so that they are
the same as they were before this change.

So this commit does not change any behavior.

config/application.rb

@@ -16,6 +16,8 @@
 
 module Gitlab
   class Application < Rails::Application
+    config.load_defaults 6.1
+
     require_dependency Rails.root.join('lib/gitlab')
     require_dependency Rails.root.join('lib/gitlab/utils')
     require_dependency Rails.root.join('lib/gitlab/action_cable/config')
@@ -37,8 +39,6 @@ class Application < Rails::Application
     require_dependency Rails.root.join('lib/gitlab/runtime')
     require_dependency Rails.root.join('lib/gitlab/patch/legacy_database_config')
 
-    config.autoloader = :zeitwerk
-
     # To be removed in 15.0
     # This preload is needed to convert legacy `database.yml`
     # from `production: adapter: postgresql`
@@ -190,11 +190,12 @@ class Application < Rails::Application
     # regardless if schema_search_path is set, or not.
     config.active_record.dump_schemas = :all
 
-    # Use new connection handling so that we can use Rails 6.1+ multiple
-    # database support.
-    config.active_record.legacy_connection_handling = false
-
-    config.action_mailer.delivery_job = "ActionMailer::MailDeliveryJob"
+    # Override default Active Record settings
+    # We cannot do this in an initializer because some models are already loaded by then
+    config.active_record.cache_versioning = false
+    config.active_record.collection_cache_versioning = false
+    config.active_record.has_many_inversing = false
+    config.active_record.belongs_to_required_by_default = false
 
     # Enable the asset pipeline
     config.assets.enabled = true
@@ -380,6 +381,7 @@ class Application < Rails::Application
     config.cache_store = :redis_cache_store, Gitlab::Redis::Cache.active_support_config
 
     config.active_job.queue_adapter = :sidekiq
+    config.action_mailer.deliver_later_queue_name = :mailers
 
     # This is needed for gitlab-shell
     ENV['GITLAB_PATH_OUTSIDE_HOOK'] = ENV['PATH']

config/initializers/action_view.rb

@@ -1,7 +0,0 @@
-# frozen_string_literal: true
-
-# This file was introduced during upgrading Rails from 5.2 to 6.0.
-# This file can be removed when `config.load_defaults 6.0` is introduced.
-
-# Don't force requests from old versions of IE to be UTF-8 encoded.
-Rails.application.config.action_view.default_enforce_utf8 = false

config/initializers/cookies_serializer.rb

@@ -2,6 +2,5 @@
 
 # Be sure to restart your server when you modify this file.
 
-Rails.application.config.action_dispatch.use_cookies_with_metadata = true
 Rails.application.config.action_dispatch.cookies_serializer =
   Gitlab::Utils.to_boolean(ENV['USE_UNSAFE_HYBRID_COOKIES']) ? :hybrid : :json

config/initializers/new_framework_defaults.rb

@@ -1,24 +0,0 @@
-# frozen_string_literal: true
-
-# Remove this `if` condition when upgraded to rails 5.0.
-# The body must be kept.
-# Be sure to restart your server when you modify this file.
-#
-# This file contains migration options to ease your Rails 5.0 upgrade.
-#
-# Once upgraded flip defaults one by one to migrate to the new default.
-#
-# Read the Guide for Upgrading Ruby on Rails for more info on each option.
-
-# Enable per-form CSRF tokens. Previous versions had false.
-Rails.application.config.action_controller.per_form_csrf_tokens = false
-
-# Enable origin-checking CSRF mitigation. Previous versions had false.
-Rails.application.config.action_controller.forgery_protection_origin_check = false
-
-# Make Ruby 2.4 preserve the timezone of the receiver when calling `to_time`.
-# Previous versions had false.
-ActiveSupport.to_time_preserves_timezone = false
-
-# Require `belongs_to` associations by default. Previous versions had false.
-Rails.application.config.active_record.belongs_to_required_by_default = false

config/initializers_before_autoloader/000_override_framework_defaults.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+# This contains configuration from Rails upgrades to override the new defaults so that we
+# keep existing behavior.
+#
+# For boolean values, the new default is the opposite of the value being set in this file.
+# For other types, the new default is noted in the comments. These are also documented in
+# https://guides.rubyonrails.org/configuring.html#results-of-config-load-defaults
+#
+# To switch a setting to the new default value, we just need to delete the specific line here.
+
+Rails.application.configure do
+  # Rails 6.1
+  config.action_dispatch.cookies_same_site_protection = nil # New default is :lax
+  config.action_dispatch.ssl_default_redirect_status = nil # New default is 308
+  ActiveSupport.utc_to_local_returns_utc_offset_times = false
+  config.action_controller.urlsafe_csrf_tokens = false
+  config.action_view.preload_links_header = false
+
+  # Rails 5.2
+  config.action_dispatch.use_authenticated_cookie_encryption = false
+  config.active_support.use_authenticated_message_encryption = false
+  config.active_support.hash_digest_class = ::Digest::MD5 # New default is ::Digest::SHA1
+  config.action_controller.default_protect_from_forgery = false
+  config.action_view.form_with_generates_ids = false
+
+  # Rails 5.1
+  config.assets.unknown_asset_fallback = true
+
+  # Rails 5.0
+  config.action_controller.per_form_csrf_tokens = false
+  config.action_controller.forgery_protection_origin_check = false
+  ActiveSupport.to_time_preserves_timezone = false
+  config.ssl_options = {} # New default is { hsts: { subdomains: true } }
+end