something.rb

  def create
    session[:user_account_params].stringify_keys!.merge!(params[:user_account]) if params[:user_account]
    session[:user_account_params]["browser_locales"] = request.env['HTTP_ACCEPT_LANGUAGE']

    @user_account = UserAccount.new(session[:user_account_params])
    @user_account.current_step = session[:user_account_step]
    if @user_account.valid?
      if params[:back_button]
        @user_account.previous_step
      elsif @user_account.last_step?
        @user_account.save if @user_account.all_valid?
      else
        @user_account.next_step
      end 
      session[:user_account_step] = @user_account.current_step
    end 
    if @user_account.new_record?
      render 'new'
    else
      session[:user_account_step] = session[:user_account_params] = nil 
      auto_login(User.find(@user_account.id))
      redirect_to "/", notice: I18n.t("registration.success")
    end 

  end