When book trees were generated, pages in chapters where ALL pages within
were not supposed to be visibile, would be visible due to the code
falling back on the raw relation which would not account for
permissions.
This has now been changed so that a custom 'visible_pages' attribute is set and used by any book tree structures, to ensure it does not fall back to the raw relation.
Added an extra test to cover.
For #2414
* Started mass-refactoring of the current entity repos
* Rewrote book tree logic
- Now does two simple queries instead of one really complex one.
- Extracted logic into its own class.
- Remove model-level akward union field listing.
- Logic now more readable than being large separate query and
compilation functions.
* Extracted and split book sort logic
* Finished up Book controller/repo organisation
* Refactored bookshelves controllers and repo parts
* Fixed issues found via phpunit
* Refactored Chapter controller
* Updated Chapter export controller
* Started Page controller/repo refactor
* Refactored another chunk of PageController
* Completed initial pagecontroller refactor pass
* Fixed tests and continued reduction of old repos
* Removed old page remove and further reduced entity repo
* Removed old entity repo, split out page controller
* Ran phpcbf and split out some page content methods
* Tidied up some EntityProvider elements
* Fixed issued caused by viewservice change
