module Rails::Railtie::Configurable::ClassMethods

def configure(&block)
  class_eval(&block)
end

def inherited(base)
  raise "You cannot inherit from a #{superclass.name} child"
end

def instance
  @instance ||= new
end

def method_missing(...)
  instance.send(...)
end

def respond_to?(*args)
  super || instance.respond_to?(*args)
end