Example of minimal authentication requirements for Rails app

application_controller.rb

ass ApplicationController < ActionController::Base
  before_action :authenticate!

  helper_method :current_user
  helper_method :user_signed_in?

  private

    def authenticate
      @current_user = nil
      authenticate_with_http_digest(Rails.application.credentials.auth_realm) do |username|
        @current_user = User.find_by(username: username)
        @current_user&.password_digest || false
      end
      !@current_user.nil?
    end

    def authenticate!
      authenticate || request_http_digest_authentication(Rails.application.credentials.auth_realm)
    end

    def current_user
      Current.user ||= @current_user
    end

    def user_signed_in?
      Current.user.present?
    end
end