Render with ``render_to_string`` a complete page within a sidekiq worker including current_user

application_helper.rb

module ApplicationHelper

  def current_user
    @current_user ||= warden.authenticate(:scope => :user)
  end

end

call_template.rb

# create the template
template = PageOfflineTemplate.new

data = template.render_to_string(
                template: "blah/my_page_to_render.html.erb",
                layout: false, 
                locals: 
                        :@current_user => user
        )
        

offline_template.rb

class OfflineTemplateController < AbstractController::Base
  include AbstractController::Logger
  include AbstractController::Rendering
  include AbstractController::Layouts
  include AbstractController::Helpers
  include AbstractController::Translation
  include AbstractController::AssetPaths
  include ActionDispatch::Routing::UrlFor
  include Rails.application.routes.url_helpers
  Rails.application.routes.default_url_options = { :host => 'www.yoursite.com' }
  # include Devise::Controllers::Helpers
  helper ApplicationHelper

  helper_method :protect_against_forgery?

  # configure the different paths correctly
  def initialize(*args)
    super()
    lookup_context.view_paths = Rails.root.join('app', 'views')
    config.javascripts_dir = Rails.root.join('public', 'javascripts')
    config.stylesheets_dir = Rails.root.join('public', 'stylesheets')
    config.assets_dir = Rails.root.join('public')
  end

  # we are not in a browser, no need for this
  def protect_against_forgery?
    false
  end

  # so that your flash calls still work
  def flash
    {}
  end

  def params
    {}
  end

  # same asset host as the controllers
  self.asset_host = ActionController::Base.asset_host
end

page_offline_template.rb

# subclass to define the @ attributes your tempalte will use
class PageOfflineTemplate < OfflineTemplate
  attr_accessor :current_user
end