- Removed old 'exposeTranslations' system to instead use new component
option system.
- Extracted validation rules into their own service provider.
- Cleaned up some formatting/comments in the repos.
Repos are generally better since otherwise we end up duplicating
things between front-end and API.
Types moved to by CONST values within a class for better visibilty
of usage and listing of types.
- Tweaked how books are passed on update to prevent unassignment if
parameter is not provided.
- Added books to validation so they show in docs.
- Added request/response examples.
- Added tests to cover.
- Added child book info to shelf info.
Review of #1908
* 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
