=== GET /books ===
[
    {
        "id": 1,
        "title": "Kotlin in Action",
        "author": "Jemerov & Isakova"
    },
    {
        "id": 2,
        "title": "Effective Kotlin",
        "author": "Marcin Moskala"
    },
    {
        "id": 3,
        "author": "Unknown"
    }
]