PermChangeTotalStock allows the user to register updates to the total stored book count.

PermGrantPermissions allows the user to grant permissions to other users.

PermLoanBooks allows the user to register book takeouts and returns.

PermManageBooks allows the user to add, edit and delete books from the library.

PermManageUsers allows the user to add, edit and delete other users.

PermQueryAvailableStock allows the user to get the number of available (not lent out) copies of a book.

PermQueryReservations allows the user to get information related to book reservations.

PermQueryTotalStock allows the user to get the total stored book count.

PermQueryUsers allows the user to get information about other users, including their permissions.

Book structure represents book entity.

BookService defines the interface for interacting with books (business logic).

BookStore defines the inteface for database interactions related to books.

Intercommunication with 'user' microservice (permission checks).