Here are the classes, structs, unions and interfaces with brief descriptions:

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Pcom
Pexample
Prestapi
Pconfig
CSwaggerConfig
Pcontroller	This package contains REST controllers for handling user, book, and borrowing operations
CBookController
CBorrowingController	Controller class providing RESTful endpoints for borrowing and returning books
CLibraryController
CUserController
Pmodel
CBook
CBorrowing	A JPA entity representing a borrowing record
CUser
Prepository
CBookRepository
CBorrowingRepository
CUserRepository
Pservice
CBookService
CBorrowingService
CUserService
Pperformance
CPerformanceTest
CRestApiApplication