The trait is supposed to be implemented on API clients.
You need to specify the [`PageTurner::PageItems`]s to
return and [`PageTurner::PageError`]s that may occur for
a particular request. Then you should implement the
[`PageTurner::turn_page`] method to describe how to
query a single page and how to prepare a request for the
next page. After that default [`PageTurner::pages`] and
[`PageTurner::into_pages`] methods become available to
provide a stream based querying API.