public Optional<Instant> getTimestamp() {
    return Optional.ofNullable(timestamp);
  }
@Test
  public void testFilePropertiesSpec_timestampSpecIso8601() throws JsonProcessingException {
    String data = "timestamp: 2020-06-08T14:54:36+00:00";

    FilePropertiesSpec parsed = mapper.readValue(data, FilePropertiesSpec.class);
    assertThat(parsed.getTimestamp().get()).isEqualTo(Instant.parse("2020-06-08T14:54:36Z"));
  }