application_controller.rb

class ApplicationController < ActionController::Base
  include Authentication
  include Authorization

  protect_from_forgery
  responders :flash

  decent_configuration do
    strategy DecentExposure::StrongParametersStrategy
  end
end

authentication.rb

module Authentication
  extend ActiveSupport::Concern

  included do
    helper do
      def current_user
        UserPresenter.new(warden.authenticate(scope: :user))
      end
    end
  end

  private

  def devise_parameter_sanitizer
    if resource_class == User
      User::ParameterSanitizer.new(User, :user, params)
    else
      super
    end
  end
end

authorization.rb

module Authorization
  extend ActiveSupport::Concern

  included do
    include Pundit
    rescue_from Pundit::NotAuthorizedError, with: :user_not_authorized
  end

  private

  def user_not_authorized
    redirect_to(root_path)
  end
end