[ci skip] Add explanation on Rack::Sendfile and fix serve static files setting.
stop looking up the reflection multiple times
join parts in `build` are *always* new, so don't bother checking
Add documentation for after_touch [ci skip]
Fix the indentation
Move define_readers to class method since it doesn't need nothing from
the instance
Move define_writers to class level since we don't need anything from the
instance
Move define_constructors to class level
Move add_counter_cache_methods to class level
Use the reflection name instead of the accessor
Push define_accessors to class level since we don't need anythig from
the instance
:scissors:
Merge pull request #12473 from claudiob/document-after-touch

Add documentation for after_touch [ci skip]
Fixing repond_with working directly on the options hash

This fixes an issue where the respond_with worked directly with the given
options hash, so that if a user relied on it after calling respond_with,
the hash wouldn't be the same.

Fixes #12029
Merge pull request #12083 from BlueHotDog/fixing_respond_with

Fixing repond_with working directly on the options hash
add dots after `Fixes #YYYYY` in actionpack CHANGELOG. [ci skip]
Expose MiddlewareStack#unshift to environment configuration.
Merge pull request #12479 from benpickles/unshift-middleware

Expose MiddlewareStack#unshift to environment configuration
Merge pull request #12283 from JuanitoFatas/rails-on-rack

[ci skip] Add explanation on Rack::Sendfile middleware in rails_on_rack.md.
observers are not part of ActiveModel [ci skip]