Enable the legacy 'Site Visibility' privacy options.
By default the privacy options form displays a single checkbox to 'discourage' search engines from indexing the site. Hooking to this action serves a dual purpose:
- Disable the single checkbox in favor of a multiple-choice list of radio buttons.
- Open the door to adding additional radio button choices to the list.
Hooking to this action also converts the 'Search Engine Visibility' heading to the more open-ended 'Site Visibility' heading.