insertPage now optionally accepts a custom slug via `data.slug`. If none is provided a slug is generated as usual based on the parent page slug and the new page title. If you override newPageSettings.html to include a text field named "slug" it just works. Leaving it blank gives you a generated slug. Naturally it would make sense to add some custom UI to autopopulate the slug field as the title is edited. For now this feature is mostly for folks who are calling insertPage programmatically and need a custom slug.