When `#perform_later` is called the locale isn't stored on the
queue, which results in a locale reset when the job is performed.
An example of the problem:
I18n.locale = 'de'
HelloJob.perform_now # german message, correct
but
I18n.locale = 'de'
HelloJob.perform_later # english message, incorrect
This PR attaches the current I18n.locale to every job during the
serialization process. It is then restored during deserialization
and used to perform the job with the correct locale.
It falls back to the default locale if no serialized locale is
found in order to provide backward compatibility with previously
stored jobs. It is not necessary to clear the queue for the update.
This adds documentation for the Active Job API. It includes
documentation on how to configure the queue_adapter, and how to create
new jobs. It adds links to the various other sections of the Active Job
documentation.
