@Override
  public Optional<Code> remove(String code) {
    return Optional.ofNullable(store.asMap().remove(code));
  }
@Test
  void remove_nonExisting() {

    Cache<String, Code> cache = Caffeine.newBuilder().build();

    var sut = new CaffeineCodeRepo(cache);

    // when
    var c1 = sut.remove("x");

    // then
    assertTrue(c1.isEmpty());
  }