```ruby
# frozen_string_literal: true

class UsersController < ApplicationController
  def edit
    @user = current_user
    @vouchers = current_user.vouchers.includes(:product, :claimed_by)
    @private_server = PrivateServer.new if @user.has_private_server_option?
  end

  def update
    if current_user.update_attributes(user_params)
      flash[:notice] = 'Settings saved'
    end
    redirect_to root_path
  end

  private

  def user_params
    params.require(:user).permit(:logs_tf_api_key, :demos_tf_api_key, :time_zone)
  end
end
```

Fix Rails 6.1 deprecation warning
user
```ruby
# frozen_string_literal: true

class UsersController < ApplicationController
  def edit
    @user = current_user
    @vouchers = current_user.vouchers.includes(:product, :claimed_by)
    @private_server = PrivateServer.new if @user.has_private_server_option?
  end

  def update
    if current_user.update(user_params)
      flash[:notice] = 'Settings saved'
    end
    redirect_to root_path
  end

  private

  def user_params
    params.require(:user).permit(:logs_tf_api_key, :demos_tf_api_key, :time_zone)
  end
end
```
assistant