220905 Optional 줄이기

public Member isPresentMemberByMemberId(Long memberId) {
    Optional<Member> optionalMember = memberRepository.findById(memberId);
    return optionalMember.orElseThrow(
             () -> new CustomException(ErrorCode.MEMBER_NOT_FOUND)
    );

는

public Member isPresentMemberByMemberId(Long memberId) {    
    return memberRepository.findById(memberId).orElseThrow(() -> new CustomException(ErrorCode.MEMBER_NOT_FOUND));

로 짧게 줄일 수 있다.