Sometimes we want to use rack_test partially instead of selenium for test speed:

```ruby
class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
  driven_by :selenium, using: :chrome, screen_size: [1400, 1400], options: {url: "http://chrome:4444/wd/hub"}
end

class WithJavaScriptTest < ApplicationSystemTestCase
end

class WithoutJavaScriptTest < ApplicationSystemTestCase
  driven_by :rack_test
end
```

In the abobe case, `WithoutJavaScriptTest` uses selenium because
`SystemTestCase` calls superclass' driver on `#initialize` (`self.class.superclass.driver.use`).

Using `class_attribute` can handle inherited `driven_by`.

Make internal methods to private

Add keep id suffix option to humanize new

No longer listens to dirs outside of the app directory.

Fix ActiveModel::Errors #keys, #values

Fix store accessors in parameters test

Before:
  person.errors.keys    # => []
  person.errors.values  # => []
  person.errors[:name]  # => []
  person.errors.keys    # => [:name]
  person.errors.values  # => [[]]

After:
  person.errors.keys   # => []
  person.errors.values # => []
  person.errors[:name] # => []
  person.errors.keys   # => []
  person.errors.values # => []

Related to #23468

make it clear how to enable caching

If a country doesn't exist in the MAPPINGS hash then create a new
`ActiveSupport::Timezone` instance using the supplied timezone id.

Fixes #28431.

The `master` changelog refer back to the `5-1-stable` changelog as a
base. No need to duplicate backported entries in the changelogs on
`master`.

With Rack::Test the headers needs to match the `HTTP_` format. The tests
were passing before because they are not asserting the response was a
cache hit.

Closes #28554

Merge pull request #28557 from y-yagi/remove_unnecessary_files_to_api_applications_when_app_task_task_executed

Remove unnecessary files to API-only Applications when `app:task` task executed

Remove -j (--javascript) option from `rails new`

Since 4.2 the default log level in production is now debug. We removed
the deprecation in c2e86584
but we don't reflected the default value. We are not appling it.

Closes #28558

Avoid converting integer as a string into float

Preprocess association query handling in predicate builder

Merge pull request #27636 from mtsmfm/disable-referential-integrity-without-superuser-privilege-take-2

Use `SET CONSTRAINTS` for `disable_referential_integrity` without superuser privileges (take 2)

fix migrate with empty version

Do not show hidden namespaces in destroy commnad help

[ci skip]

Prevent ujs event propagation if element disabled when event chain begins

ignore system test gems on Gemfile when execute with --skip-test option

Add stronger assertions to rake migration tasks to make sure the user is providing a numeric VERSION
An empty string was getting converted to version = 0. This would in turn pass the presence check.

Address linting warning

Add test for rake task and refactor code to meet expectations
In particular passing VERSION=0 should not raise an error.

Addressed Comments for PR #28485. Trimmed empty lines + change of wording for error message

Adjust test for change of wording in error message

Change condition to follow rails idioms

This is a follow up to a6d065e3. When using `form_with` you must supply
field ids manually. Since the scaffold generator is using labels we
need to make sure that they are linked up properly.

Re-create https://github.com/rails/rails/pull/21233

eeac6151 was reverted (127509c0) because it breaks tests.

----------------

ref: 72c15572

- We must use `authors` fixture with `author_addresses` because of its foreign key constraint.
- Tests require PostgreSQL >= 9.4.2 because it had a bug about `ALTER CONSTRAINTS` and fixed in 9.4.2.

"3 Days before release" should an h2, like the rest of the day headings.
All of the steps are h3 tags.

[ci skip]

Add apostrophe.

[ci skip]

Add necessary commas.

[ci skip]

Taken from `bin/rails about` run on a v5.1.0.rc1 application.

[ci skip]

RC1 is out, `5-1-stable` has been created, figured it was time to start
updating this stuff :)

[ci skip]

[ci skip]