Sidekiq autoload

[nunommc]

🔧 Changes

• autoloads Sidekiq custom middleware if Sidekiq is present;

Initializers won't need to call require 'acts_as_tenant/sidekiq' anymore, that can be removed from any repos once these changes are released.

[excid3]

I adjusted this to delay the Sidekiq integration until after ActiveRecord is loaded to ensure Sidekiq was already required in the parent application.