`relation.exists?` just wants to know if there is a result or not, does
not need the exact records matched. Therefore, an intermediate SELECT
query for eager loading is not necessary.

Fix :inverse_of documentation

[ci skip] setting :inverse_of works with :as, :through and :polymorphic options, and is needed for bi-directionality with a scope

[ci skip] Remove :conditions opion from association basics guide

This got replaced by scopes.

Need reloading when through record has replaced.

Clean up railties tests

Merge pull request #16314 from zoltankiss/allow-nested-has-many-associations-on-unpersisted-parent-instances

fix nested `has many :through` associations on unpersisted parent instances

  Remove `AppGeneratorTest#test_active_storage_install`.
  The test is added by 67db41aa,
  since #31534 this test doesn't test anything.

  Remove redundant assertions in `SharedGeneratorTests`.
  These assertions is added by 4a835aa3.
  Follows 67db41aa, #31534.

I removed redundant `Array.wrap(records)` since `Preloader` is nodoc
class and Active Record always pass `records` as an array to
`Preloader`.
But if users relies on that behavior, it is not worth dropping its
behavior.

Fixes #31661.

Fix performance issue with NameError#missing_name on ruby >= v2.3.0.

Consistency between first() and last() with limit

Don't include Active Storage migrations in new apps

Change Active Storage destroy callbacks

There is concern that only blob are deleted depending on
the `before_destroy` definition order which throws abort.

To pick up 21417e02

Brought to you by a 12 year old Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=329509

Explicitly declare inverse associations so ActiveStorage::Attachment touches the original record instance.

Closes #31542.

Allow overriding filename in `Blob#service_url`

This is useful when we have several representations for the same
underlying file, each one with a different name, and we need to provide
a custom download URL based on that name and not that of the underlying
file.

Fix rubocop space before comma

`ActiveSupport::OrderedOptions` responds to any message.

Merge pull request #31547 from eugeneius/use_authenticated_message_encryption_new_framework_defaults

Allow use_authenticated_message_encryption to be set in new_framework_defaults_5_2.rb

Enabling this option in new_framework_defaults_5_2.rb didn't work
before, as railtie initializers run before application initializers.

Using `respond_to?` to decide whether to set the option wasn't working
either, as `ActiveSupport::OrderedOptions` responds to any message.

Improve the deprecation message for using subclass of Rails::Application to start the Rails server

Currently deleting through records doesn't respect `source_type`. It
should not be ignored in that case.

Related #23209.
Fixes #24116.