Fix broken RDoc formatting

The `@` ivar format doesn’t work with RDoc's `+` code formatting; needs `<tt>`.

[ci skip]

Fix engine command

Use the same key as presented in doc

Fix non escaped character

Add missed `require`

ActiveStorage:Filter out Minitest backtrace.

Simplify `git_source` in Gemfile

Deprecate ActionDispatch::TestResponse response aliases

Remove needless restoring of `default_charset`

Merge pull request #30115 from intrip/30049-application-controller-renderer-defaults-automatic-reload-in-dev

Fix ApplicationController.renderer.defaults overriding in development

Ref: https://github.com/rails/rails/blob/a8217bb594a625fb46a6af1488c0bde4aeac4986/railties/lib/rails/generators/rails/app/templates/config/storage.yml#L24

add missing collection.reload documentation [ci skip]

Fix random CI failure due to non-deterministic sorting order

Fix dummy_app configuration

Use `with_dummy_app?` in gitignore

Set ActiveStorage::Blob.service when ActiveStorage::Blob is loaded

This module has behavior that is not present in `ActiveModel::Dirty`,
which is intended to be public API.

add reload_association to documentation

Deprecate support of older `config.ru`

Fixes that ActiveStorage::Blob.service is unset when ActiveStorage::Blob
is reloaded.

Support content_type in AzureStorageService#url

* Add migrations per rails engine conventions

* Fix failing tests

Add in the content_type option, which is defined as part of the generic
ActiveStorage::Service class.

Without this option, attempts to generate a URL for an attached file
fail with "ArgumentError (unknown keyword: content_type)"

It should be sorted to be deterministic executed result.

```
% bundle exec rake test_postgresql --verbose TESTOPTS="--seed=52812"

(snip)

Failure:
HasManyThroughAssociationsTest#test_has_many_association_through_a_has_many_association_to_self [/Users/kamipo/src/github.com/rails/rails/activerecord/test/cases/associations/has_many_through_associations_test.rb:820]:
--- expected
+++ actual
@@ -1 +1 @@
-[#<Person id: 85, primary_contact_id: 84, gender: "M", number1_fan_id: 1, lock_version: 0, comments: nil, followers_count: 0, friends_too_count: 0, best_friend_id: nil, best_friend_of_id: nil, insures: 0, born_at: nil, created_at: "2017-08-08 07:33:52", updated_at: "2017-08-08 07:33:52", first_name: "John">, #<Person id: 1, primary_contact_id: 2, gender: "M", number1_fan_id: 3, lock_version: 0, comments: nil, followers_count: 1, friends_too_count: 1, best_friend_id: nil, best_friend_of_id: nil, insures: 0, born_at: nil, created_at: "2017-08-08 07:33:49", updated_at: "2017-08-08 07:33:49", first_name: "Michael">, #<Person id: 3, primary_contact_id: 2, gender: "F", number1_fan_id: 1, lock_version: 0, comments: nil, followers_count: 1, friends_too_count: 1, best_friend_id: nil, best_friend_of_id: nil, insures: 0, born_at: nil, created_at: "2017-08-08 07:33:49", updated_at: "2017-08-08 07:33:49", first_name: "Susan">]
+#<ActiveRecord::Associations::CollectionProxy [#<Person id: 1, primary_contact_id: 2, gender: "M", number1_fan_id: 3, lock_version: 0, comments: nil, followers_count: 1, friends_too_count: 1, best_friend_id: nil, best_friend_of_id: nil, insures: 0, born_at: nil, created_at: "2017-08-08 07:33:49", updated_at: "2017-08-08 07:33:49", first_name: "Michael">, #<Person id: 3, primary_contact_id: 2, gender: "F", number1_fan_id: 1, lock_version: 0, comments: nil, followers_count: 1, friends_too_count: 1, best_friend_id: nil, best_friend_of_id: nil, insures: 0, born_at: nil, created_at: "2017-08-08 07:33:49", updated_at: "2017-08-08 07:33:49", first_name: "Susan">, #<Person id: 85, primary_contact_id: 84, gender: "M", number1_fan_id: 1, lock_version: 0, comments: nil, followers_count: 0, friends_too_count: 0, best_friend_id: nil, best_friend_of_id: nil, insures: 0, born_at: nil, created_at: "2017-08-08 07:33:52", updated_at: "2017-08-08 07:33:52", first_name: "John">]>
```

[ci skip] Update action_mailer_basics.md

In some examples and guides we are recommending to use code like:

```ruby
verified_user = User.find_by(id: cookies.signed[:user_id])
```

My suggestion is to use instead:

```ruby
verified_user = User.find_by(id: cookies.encrypted[:user_id])
```

which invites users to prefer the "newer" encrypted cookies over the
"legacy" signed cookies.

Since Rails 4.0, `config.ru` generated by default uses instances of
`Rails.application`.  Therefore, I think that it is good to deprecate
the old behavior.

Related: #9669

* Extend image_tag to accept ActiveStorage's Attachments and Variants

* Flip resolve_image_source around

* Add tests for the new use-cases of image_tag

* Remove the higher-level test

* Update image_tag documentation

* Add error states into the test suite

* Re-raise polymorhic_url's NoMethodError as ArgumentError

* delegate_missing_to will raise DelegationError instead of NoMethodError

Filter out Minitest backtrace while allowing backtrace from other
libraries to be shown.

Follow up of https://github.com/rails/rails/commit/0b8441bd415c444b8d4afbfc93af79ec7677aa2c

`ActiveRecord::ConnectionAdapters::QueryCache::ConnectionPoolConfiguration`
depends on `Concurrent::Map`.

https://github.com/rails/rails/issues/30072

Should _probably_ be done across the board with all of our
documentation, but going to leave that for another time :)

[ci skip]