docs: public boolean contains(final LocalDate date) {
          if (date == null){
              return false;
          }
          if (endDate() == null) {
              if (startDate() == null) {
                  return true;
              }
              if (date.isEqual(startDate()) || date.isAfter(startDate())) {
                  return true;
              }
              return false;
          }
          return asInterval().contains(date.toInterval());
      }