Avoid adding new method to `ActiveSupport`.

We don't need this delegation and can be setting directly to the right
object.

Also document the new configuration.

activesupport/lib/active_support/core_ext/digest.rb

@@ -1,9 +1,3 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/digest/uuid"
-
-module ActiveSupport
-  class << self
-    delegate :use_rfc4122_namespaced_uuids, :use_rfc4122_namespaced_uuids=, to: :'Digest::UUID'
-  end
-end

activesupport/lib/active_support/railtie.rb

@@ -133,7 +133,7 @@ module ActiveSupport
       config.after_initialize do
         if app.config.active_support.use_rfc4122_namespaced_uuids
           require "active_support/core_ext/digest"
-          ActiveSupport.use_rfc4122_namespaced_uuids = app.config.active_support.use_rfc4122_namespaced_uuids
+          ::Digest::UUID.use_rfc4122_namespaced_uuids = app.config.active_support.use_rfc4122_namespaced_uuids
         end
       end
     end

activesupport/test/core_ext/digest/uuid_test.rb

@@ -4,14 +4,6 @@ require_relative "../../abstract_unit"
 require "active_support/core_ext/digest"
 
 class DigestUUIDExt < ActiveSupport::TestCase
-  def with_use_rfc4122_namespaced_uuids_set
-    old_value = ActiveSupport.use_rfc4122_namespaced_uuids
-    ActiveSupport.use_rfc4122_namespaced_uuids = true
-    yield
-  ensure
-    ActiveSupport.use_rfc4122_namespaced_uuids = old_value
-  end
-
   def test_constants
     assert_equal "6ba7b810-9dad-11d1-80b4-00c04fd430c8", "%08x-%04x-%04x-%04x-%04x%08x" % Digest::UUID::DNS_NAMESPACE.unpack("NnnnnN")
     assert_equal "6ba7b811-9dad-11d1-80b4-00c04fd430c8", "%08x-%04x-%04x-%04x-%04x%08x" % Digest::UUID::URL_NAMESPACE.unpack("NnnnnN")
@@ -184,4 +176,13 @@ class DigestUUIDExt < ActiveSupport::TestCase
       Digest::UUID.uuid_from_hash(OpenSSL::Digest::SHA256, Digest::UUID::OID_NAMESPACE, "1.2.3")
     end
   end
+
+  private
+    def with_use_rfc4122_namespaced_uuids_set
+      old_value = Digest::UUID.use_rfc4122_namespaced_uuids
+      Digest::UUID.use_rfc4122_namespaced_uuids = true
+      yield
+    ensure
+      Digest::UUID.use_rfc4122_namespaced_uuids = old_value
+    end
 end

guides/source/configuring.md

@@ -1729,6 +1729,7 @@ Accepts a string for the HTML tag used to wrap attachments. Defaults to `"action
 - `config.active_support.cache_format_version`: `7.0`
 - `config.active_support.remove_deprecated_time_with_zone_name`: `true`
 - `config.active_support.executor_around_test_case`: `true`
+- `config.active_support.use_rfc4122_namespaced_uuids`: `true`
 - `config.action_dispatch.return_only_request_media_type_on_content_type`: `false`
 - `config.action_controller.silence_disabled_session_errors`: `false`
 - `config.action_mailer.smtp_timeout`: `5`
@@ -1816,6 +1817,7 @@ Accepts a string for the HTML tag used to wrap attachments. Defaults to `"action
 - `config.active_support.key_generator_hash_digest_class`: `OpenSSL::Digest::SHA1`
 - `config.active_support.cache_format_version`: `6.1`
 - `config.active_support.executor_around_test_case`: `false`
+- ``config.active_support.use_rfc4122_namespaced_uuids``: `false`
 - `config.action_dispatch.return_only_request_media_type_on_content_type`: `true`
 - `ActiveSupport.utc_to_local_returns_utc_offset_times`: `false`
 - `config.action_mailer.smtp_timeout`: `nil`

railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_7_0.rb.tt

@@ -97,3 +97,10 @@
 # Previously this was set in an initializer. It's fine to keep using that initializer if you've customized it.
 # To disable parameter wrapping entirely, set this config to `false`.
 # Rails.application.config.action_controller.wrap_parameters_by_default = true
+
+# Specifies whether generated namespaced UUIDs follow the RFC 4122 standard for namespace IDs provided as a
+# `String` to `Digest::UUID.uuid_v3` or `Digest::UUID.uuid_v5` method calls.
+#
+# See https://guides.rubyonrails.org/configuring.html#config-active-support-use-rfc4122-namespaced-uuids for
+# more information
+# Rails.application.config.active_support.use_rfc4122_namespaced_uuids = true

railties/test/application/configuration_test.rb

@@ -2422,18 +2422,18 @@ module ApplicationTests
       assert_equal 1234, ActiveSupport.test_parallelization_threshold
     end
 
-    test "ActiveSupport.use_rfc4122_namespaced_uuids is enabled by default for new apps" do
+    test "Digest::UUID.use_rfc4122_namespaced_uuids is enabled by default for new apps" do
       app "development"
 
-      assert_equal true, ActiveSupport.use_rfc4122_namespaced_uuids
+      assert_equal true, Digest::UUID.use_rfc4122_namespaced_uuids
     end
 
-    test "ActiveSupport.use_rfc4122_namespaced_uuids is disabled by default for upgraded apps" do
+    test "Digest::UUID.use_rfc4122_namespaced_uuids is disabled by default for upgraded apps" do
       remove_from_config '.*config\.load_defaults.*\n'
 
       app "development"
 
-      assert_equal false, ActiveSupport.use_rfc4122_namespaced_uuids
+      assert_equal false, Digest::UUID.use_rfc4122_namespaced_uuids
     end
 
     test "custom serializers should be able to set via config.active_job.custom_serializers in an initializer" do