정렬 방향 asc dec

/api/posts?pageNo=1&pageSize=5&sortBy=id&sortDir=dec

1. 컨트롤러

	@GetMapping
	public PostResponse getAllPosts(
				@RequestParam(value = "pageNo", defaultValue = "0", required = false) int pageNo , 
				@RequestParam(value = "pageSize", defaultValue = "10", required = false) int pageSize,
				@RequestParam(value = "sortBy", defaultValue = "id", required = false) String sortBy,
				@RequestParam(value = "sortDir", defaultValue = "asc", required = false) String sortDir
	){
		return postService.getAllPosts(pageNo, pageSize, sortBy, sortDir);
	}

2. PostService

	//모든 포스트들을 가져오기 (페이지네이션&sorting)
	PostResponse getAllPosts(int pageNo, int pageSize, String sortBy, String sortDir);

3. PostServiceImple

	@Override
	public PostResponse getAllPosts(int pageNo, int pageSize, String sortBy, String sortDir) {
		
		Sort sort = sortDir.equalsIgnoreCase(Sort.Direction.ASC.name()) ? 
				Sort.by(sortBy).ascending() : Sort.by(sortBy).descending(); 
		//Pageable 객체 생성
		Pageable pageable = PageRequest.of(pageNo, pageSize, ?);