feat: 새로 정의한 커스텀 예외 필드 notnull 변경 및 예외 응답 객체 추가

src/main/kotlin/roomescape/auth/exception/AuthException.kt

@@ -4,5 +4,5 @@ import roomescape.common.exception.RoomException
 
 class AuthException(
         override val errorCode: AuthErrorCode,
-        override val message: String? = errorCode.message
+        override val message: String = errorCode.message
 ) : RoomException(errorCode, message)

src/main/kotlin/roomescape/common/dto/response/CommonApiResponse.kt

@@ -1,6 +1,7 @@
 package roomescape.common.dto.response
 
 import com.fasterxml.jackson.annotation.JsonInclude
+import roomescape.common.exception.ErrorCode
 import roomescape.common.exception.ErrorType
 
 @JsonInclude(JsonInclude.Include.NON_NULL)
@@ -12,3 +13,13 @@ data class CommonErrorResponse(
         val errorType: ErrorType,
         val message: String? = errorType.description
 )
+
+data class CommonErrorResponseV2(
+        val code: String,
+        val message: String
+) {
+    constructor(errorCode: ErrorCode, message: String = errorCode.message) : this(
+            code = errorCode.errorCode,
+            message = message
+    )
+}

src/main/kotlin/roomescape/common/exception/RoomException.kt

@@ -2,5 +2,5 @@ package roomescape.common.exception
 
 open class RoomException(
         open val errorCode: ErrorCode,
-        override val message: String? = errorCode.message
+        override val message: String = errorCode.message
 ) : RuntimeException(message)