Remove requirement on mathn

Fix `default_scoped` with defined `default_scope` on STI model

load_schema! is overridden by attribute modules, so we need to wait
until it has returned.

Support PostgreSQL 10 `pg_sequence`

see: https://bugs.ruby-lang.org/issues/6696

some typos and rephrasing in system test guide [ci skip]

SystemTesting::Driver can register capybara-webkit and poltergeist

Replace an outdated mention of `jquery_ujs` with `rails-ujs`

Fix regression in Numericality validator

Add missing `delegate :extending, to: :all`

Fix association with extension issues

Fix UUID column with `null: true` and `default: nil`

Check for jQuery ajax

round before calculating exponent in number_to_human_converter

[5.1 Backport] Fix edge guides for Active Record callbacks

[ci skip]

Doc updates for ActiveRecord::Batches

Update to Rails ujs readme

Do not show --webpack option in the plugin help message

Add a Monitor to ModelSchema#load_schema

Make `secrets:edit` run `secrets:setup` if it hasn't already.

Fix crashing on circular left join references with scoping

Both reference id and type should be `NOT NULL` if `null: false` is specified

Set `Capybara.app_host` through `host!`

Remove rubygems version lock

Remove obsolete Guides source files [ci skip]

Fix broken external link in security guide.

Update 'Rails on Rack' guide [ci skip]

Update information on using Gmail when 2FA is in use [ci skip]

Update Rails API Application guide to match current code [ci skip]

Fix implicit calculations with scalars and durations

Fixed Frozen string error in actionpack

Set non 0 value to logger not to be affected by Ruby versions

The object inside the scope is of the class that define the association
not the associated class.

[ci skip]

Message encryptor auth tag check

Fixes MessageEncryptor when used in AEAD mode. Specifically, we need to check if the `auth_tag` is nil. This may arise when an AEAD encryptor is used to decrypt a ciphertext generated from a different mode, such as CBC-HMAC. Basically, the number of double dashes will differ and `auth_tag` may be nil in this case.

Previously this implied that system tests provided other non-headless
drivers when Selenium is the only driver that uses `:using`,
`:screen_size` or `:options` arguments.

This change clarifies that Selenium is the only non-headless driver.

It's more likely you'll generate a test for testing users than a users
creates test. This is a better example of a real world test.
Additionally the users create view is unlikely to have the text
"UserCreates" since that is likely generated as well. This is now an
example of visiting the users index.