Thank you @fxn :green_heart::yellow_heart::heart::purple_heart::blue_heart:

[ci skip]

Extract a Subscriber base class from LogSubscriber

Adds a ActiveSupport::Subscriber base class that LogSubscriber inherits
from. By inheriting from Subscriber, other kinds of subscribers can take
advantage of the event attachment system.

We tend to use Markdown for everything but the API, the
README is no longer used as the home page of the API
after 7a5aa720, so we can now migrate it.

replace match with get verb in ActionController::Metal

[ci skip]

[ci skip]

Fixed typos in AR CHANGELOG

db:test:load task should be favored over db:test:load_schema, because it
checks for chosen format (ActiveRecord::Base.schema_format).

closes #10227

Make [] method more readable

Fix bit string problem

This reverts commit cdd293cb.

Reason: This wasn't properly fix.

Use strip_heredoc where possible

AR postgres binary bug fix

interpolate instead of string concat

Add documentation for `collection.create!` on has_many records. [ci skip]

this shows a problem with nil values

use define_singleton_method instead of class_eval

Add :nodoc: mark to PerThreadRegistry#method_missing [ci skip]

Update github links

Existing code was delegating to the instance with delegate
macro calls, or invoking the instance method to reach
the object and call its instance methods.

But the point is to have a clean class-level interface where
the thread local instance is hidden in the implementation.

References #11c69738.
References #10198.

remove unused variable

Registries have class-level accessors to write clean code, let's
use them. This makes style uniform also with existing usage in
ScopeRegistry and InstrumentationRegistry.

If performance of the method_missing callback was ever considered to
be a concern, then we should stop using it altogether and probably
remove the callback. But while we have the feature we should use it.

The previous version was kind of duplicating the documentation of
AS::PerThreadRegistry. Just say how to use it, the thread locals
registry is know part of our vocabulary (though a pointer to
Active Support is added for reference).

* It focuses on how to use it.

* Removes some ambigueties in the original docs about whether the state is stored in the class.

* Documents it provides class-level accessors via method_missing.

* Documents that if the extended class has an initializer, it must accept no arguments.