Refactored enums
Enums now produce full URLs, direct interaction with builder not required
Included support for deserializing books
Improved exception handling for book deserialization
Added tests for books/builders
Added lots of tests & test data, for URLs and books
Refactored url building further
Added missing new exception
Cleanup/refactor of BookListBuilder
Added more exceptions
Updated tests
More refactor and de-linting of BookBuilder
Added more negative case tests