You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: omniauth_callbacks_controller.rb
    path of file: ./repos/boring_generators/lib/generators/boring/oauth/twitter/install/templates
    
    the code of the file until where you have to start completion: class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  # See https://github.com/omniauth/omniauth/wiki/FAQ#rails-session-is-clobbered-after-callback-on-develop
    
  def twitter
    # You need to implement the method below in your model (e.g. app/models/user.rb)
    @user = User.from_omniauth(request.env["omniauth.auth"])

    if @user.persisted?
      sign_in_and_redirect @user, event: :authentication #this will throw if @user is not activated
      set_flash_message(:notice, :success, kind: "Twitter") if is_navigational_format?
    else
      session["devise.twitter_data"] = request.env["omniauth.auth"].except(:extra) # Removing extra as it can overflow some session stores
      redirect_to new_user_registration_url
    end