Created a generic list formatting helper class for this, to align with
logic used on the search results endpoint and for easier future re-use
in a standardised way.
Also updated some class property types.
Added test to cover new books-contents results.
Related to #3734
- Fixed page editor default focus not working as expected due to
misnamed attribute.
- Added owned_by to relevant areas of the API including the docs.
- Made book relation on page accessible even if deleted since it could cause an issue on views, such as audit trail, when the relation is accessed when the book is deleted.
- 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
