[postgres] include PgArrayParser directly

[ci skip] Fix two factual errors and highlight code in generators guide.

[Fixes #15064] Calling number_to_delimited on a ActiveSupport::SafeBuffer results in mangled output

Update and add tests in array_ext_test.rb

Remove falsy deprecation note in AS guides [ci skip]

This is no longer true as @jeremy removed the deprecation in 7a5601c4.

Do not check defined?(CGI) on every call #to_query

Dup options hash to prevent modifications

* by default composite types are mapped as `OID::Identity` and issue a warning
* the user is advised to register his own `OID::Type` to make use of composite types

Registering a new `OID::Type` does currently not allow to specify the type casting
behavior when writing to the database. In order for it to work we need to use the
values within `@attributes`. They are already being type casted and are ready to be
written to the DB.

See https://github.com/rails/rails/blob/57643c961feb24b662620d330e71103a830003e8/activerecord/lib/active_record/attribute_methods.rb#L460-L462

It's usage has been removed in 325c9d5e.

`options[:default]` and `options[:raise]` can be mistakenly added to the `options` hash. This can be a problem if you're reusing the same object.

Fix regression on `assert_redirected_to`.

Use with_translation helper to clean up I18n stored translations.

Clean up deliveries after each test.

Do not clear deliveries in setup.

A minor stylistic fix and cleanup of mail deliveries.

`assert_redirected_to` would fail if there is no controller set on
a `ActionDispatch::IntegrationTest`, as _compute_redirect_to_location
would be called on the controller to build the url.

This regression was introduced after 1dacfbab.

[fixes #14691]