`strip_heredoc` method is defined on active_support/core_ext/string

Small grammar fix in pluck description

Do not depend on queue_classic on JRuby

4.2 Release Notes pass [ci skip]

[ci skip] config.active_record.errors_in_transactional_callbacks -> config.active_record.raise_in_transactional_callbacks

[ci skip] Update plugin doc with the latest rails

[ci skip] Removed unnecessary word from Getting Started

[ci skip] config.active_record.errors_in_transactional_callbacks -> config.active_record.raise_in_transactional_callbacks

Make sure :checkout_timeout and :dead_connection_timeout are numbers
Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

Remove to_s from reflection.type in add_constraints

The instance var is already saved as a string in the initialization
method of AssociationReflection.

See https://github.com/rails/rails/blob/master/activerecord/lib/active_record/reflection.rb#L273

Fix after_commit warning message

Fix broken link to Upgrading Ruby on Rails Guide [ci skip]

in the 4.2 Release Notes [skip ci]

Change to link suggested by @zzak [skip ci]

Fixes #15821.

Add activejob guide to documents.yml [ci skip]

[ActiveJob] Add queue_name_prefix

fix broken link to rails blog [ci skip]

We can split queues on a per environement basis as well as seggregate per application so we can split queues on a per env basis

ActiveJob::Base.queue_name_prefix = 'foo'

Add option to stop swallowing errors on callbacks.