> POST /books  {"isbn":"978-0134685991","title":"Effective Java","author":"Joshua Bloch","copies":2}
{"id":1,"isbn":"978-0134685991","title":"Effective Java","author":"Joshua Bloch","totalCopies":2,"availableCopies":2}
< HTTP 201

> POST /books  {"isbn":"978-0596009205","title":"Head First Java","author":"Kathy Sierra","copies":1}
{"id":2,"isbn":"978-0596009205","title":"Head First Java","author":"Kathy Sierra","totalCopies":1,"availableCopies":1}
< HTTP 201

> POST /books  {"isbn":"","title":"","author":"Nobody","copies":0}
{"detail":"request body failed validation","instance":"/api/books","status":400,"title":"Bad Request","errors":{"copies":"must be greater than or equal to 1","isbn":"must not be blank","title":"must not be blank"}}
< HTTP 400

> POST /members  {"name":"Asha","email":"asha@example.com"}
{"id":1,"name":"Asha","email":"asha@example.com"}
< HTTP 201

> POST /members  {"name":"Ravi","email":"not-an-email"}
{"detail":"request body failed validation","instance":"/api/members","status":400,"title":"Bad Request","errors":{"email":"must be a well-formed email address"}}
< HTTP 400

> POST /members  {"name":"Ravi","email":"ravi@example.com"}
{"id":2,"name":"Ravi","email":"ravi@example.com"}
< HTTP 201

> POST /loans  {"memberId":1,"bookId":2}
{"id":1,"bookTitle":"Head First Java","memberName":"Asha","borrowedOn":"2026-11-14","dueOn":"2026-11-28","returnedOn":null,"fine":0}
< HTTP 201

> POST /loans  {"memberId":2,"bookId":2}
{"detail":"no copies of 'Head First Java' are available","instance":"/api/loans","status":409,"title":"Conflict"}
< HTTP 409

> POST /loans/1/return
{"id":1,"bookTitle":"Head First Java","memberName":"Asha","borrowedOn":"2026-11-14","dueOn":"2026-11-28","returnedOn":"2026-11-14","fine":0}
< HTTP 200

> GET /books
[{"id":1,"isbn":"978-0134685991","title":"Effective Java","author":"Joshua Bloch","totalCopies":2,"availableCopies":2},{"id":2,"isbn":"978-0596009205","title":"Head First Java","author":"Kathy Sierra","totalCopies":1,"availableCopies":1}]
< HTTP 200