Serialize classes and modules with ActiveJob

[kddnewton]

This commit allows ActiveJob to serialize classes and modules without a custom serializer. This allows for workflows like:

class EmailJob < ApplicationJob
  queue_as :default
  def perform(template_class, *arguments)
    template_class.new(*arguments).send!
  end
end

module Email
  class FooTemplate ... end
  class BarTemplate ... end
end

EmailJob.perform_later(Email::FooTemplate, ...)
EmailJob.perform_later(Email::BarTemplate, ...)

Currently this is only achieveable through a custom serializer or through constantizing in each instance.

[kaspth]

LGTM, thanks!