@Override
  public void save(@NonNull Session session) {
    if (session.id() == null) {
      throw new IllegalArgumentException("session has no ID");
    }

    store.put(session.id(), session);
  }
@Test
  void save_noId() {
    var sut = new CaffeineSessionRepo(null, Duration.ofMinutes(5));
    var session = new Session(null, null, null, null, null, null, null, null, null);

    assertThrows(IllegalArgumentException.class, () -> sut.save(session));
  }