Cannot enable Wiki Page events from Webhook admin UI in a Project
Wiki Page events was introduced by !2998 (merged) as part of the work for #4233 (closed) While it has been added most to support the Slack service template, it lacked the UI components to enable it arbitrarily to any project.
Implementing that will help with #563 (moved).
We cannot close the issue yet, as the hook data we are sending is not 100% correct (we send details of the project, but should also send details of the "ProjectWiki" attributes like URLs and repositories relative to the wiki itself). See #17507 (closed)