Tracking failed logins with Devise

devise_failed_login.rb

# routes.rb
Rails.application.routes.draw do
  devise_for :users, controllers: { sessions: 'sessions' }
end

# sessions_controller.rb
class SessionsController < Devise::SessionsController
  protected

  def auth_options
    # find the email field
    key = serialize_options(resource)[:methods].first
    email = sign_in_params[key]

    # find the user if any
    user = resource_class.find_for_authentication(key => email)

    # make it available to Warden hooks
    super.merge(email: email, user_id: user && user.id)
  end
end

# config/initializers/warden.rb
Warden::Manager.before_failure do |env, opts|
  if opts[:action] == 'unauthenticated'
    castle = env['castle']

    begin
      castle.track(
        event: '$login.failed',
        user_id: opts[:user_id],
        properties: {
          email: opts[:email]
        }
      )
    rescue ::Castle::Error
    end
  end
end