feat: 커스텀 예외 및 에러 코드/응답 구현 (#19)

* feat: 에러 코드 구현

* feat: 커스텀 예외 구현

* feat: 예외 응답 구현

src/main/java/com/depromeet/global/error/ErrorResponse.java

@@ -0,0 +1,16 @@
+package com.depromeet.global.error;
+
+import java.time.LocalDateTime;
+
+import org.springframework.http.HttpStatus;
+
+public record ErrorResponse(
+	int status,
+	String message,
+	LocalDateTime timestamp
+) {
+
+	public static ErrorResponse of(HttpStatus status, String message) {
+		return new ErrorResponse(status.value(), message, LocalDateTime.now());
+	}
+}

src/main/java/com/depromeet/global/error/exception/CustomException.java

@@ -0,0 +1,11 @@
+package com.depromeet.global.error.exception;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class CustomException extends RuntimeException {
+
+	private final ErrorCode errorCode;
+}

src/main/java/com/depromeet/global/error/exception/ErrorCode.java

@@ -0,0 +1,17 @@
+package com.depromeet.global.error.exception;
+
+import org.springframework.http.HttpStatus;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public enum ErrorCode {
+
+	SAMPLE_ERROR(HttpStatus.BAD_REQUEST, "Sample Error Message"),
+	;
+
+	private final HttpStatus status;
+	private final String message;
+}