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

> POST /api/books  {"isbn":"978-0134685991","title":"Effective Java","author":"Joshua Bloch","copies":2}
< 409  {"detail":"ISBN 978-0134685991 already exists","instance":"/api/books","status":409,"title":"Conflict"}

> POST /api/books  {"isbn":"978-0000000000","title":"","author":"Nobody","copies":0}
< 400  {"detail":"request body failed validation","instance":"/api/books","status":400,"title":"Bad Request","errors":{"copies":"must be greater than or equal to 1","title":"must not be blank"}}

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

> POST /api/books  {"isbn":"978-0132350884","title":"Clean Code","author":"Robert Martin","copies":1}
< 201  {"id":3,"isbn":"978-0132350884","title":"Clean Code","author":"Robert Martin","totalCopies":1,"availableCopies":1}

> POST /api/books  {"isbn":"978-0321356680","title":"Effective Java 2e","author":"Joshua Bloch","copies":1}
< 201  {"id":4,"isbn":"978-0321356680","title":"Effective Java 2e","author":"Joshua Bloch","totalCopies":1,"availableCopies":1}

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

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

> POST /api/loans  {"memberId":1,"bookId":2}
< 201  {"id":1,"bookTitle":"Head First Java","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0}

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

> POST /api/loans  {"memberId":99,"bookId":1}
< 404  {"detail":"no member with id 99","instance":"/api/loans","status":404,"title":"Not Found"}

> POST /api/loans/1/return  {"returnedOn":"2026-11-20"}
< 200  {"id":1,"bookTitle":"Head First Java","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":"2026-11-20","fine":10}

> POST /api/loans/1/return  {"returnedOn":"2026-11-21"}
< 409  {"detail":"loan 1 was already returned on 2026-11-20","instance":"/api/loans/1/return","status":409,"title":"Conflict"}

> POST /api/loans  {"memberId":1,"bookId":1}
< 201  {"id":2,"bookTitle":"Effective Java","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0}

> POST /api/loans  {"memberId":1,"bookId":3}
< 201  {"id":3,"bookTitle":"Clean Code","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0}

> POST /api/loans  {"memberId":1,"bookId":4}
< 201  {"id":4,"bookTitle":"Effective Java 2e","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0}

> POST /api/loans  {"memberId":1,"bookId":2}
< 422  {"detail":"Asha already has 3 active loans (max 3)","instance":"/api/loans","status":422,"title":"Unprocessable Content"}

> GET /api/books
< 200  [{"id":1,"isbn":"978-0134685991","title":"Effective Java","author":"Joshua Bloch","totalCopies":2,"availableCopies":1},{"id":2,"isbn":"978-0596009205","title":"Head First Java","author":"Kathy Sierra","totalCopies":1,"availableCopies":1},{"id":3,"isbn":"978-0132350884","title":"Clean Code","author":"Robert Martin","totalCopies":1,"availableCopies":0},{"id":4,"isbn":"978-0321356680","title":"Effective Java 2e","author":"Joshua Bloch","totalCopies":1,"availableCopies":0}]

> GET /api/loans
< 200  [{"id":1,"bookTitle":"Head First Java","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":"2026-11-20","fine":10},{"id":2,"bookTitle":"Effective Java","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0},{"id":3,"bookTitle":"Clean Code","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0},{"id":4,"bookTitle":"Effective Java 2e","memberName":"Asha","borrowedOn":"2026-11-01","dueOn":"2026-11-15","returnedOn":null,"fine":0}]