[Feat/#70] 사용자 초대 코드 조회 API 구현 (#71)

## 📌 관련 이슈
- close #70 

## ✨ 변경 사항
- 사용자 초대 코드 조회 API 추가

Author: SeHyeonCho

src/main/java/com/swyp/server/domain/user/controller/UserController.java

@@ -1,5 +1,6 @@
 package com.swyp.server.domain.user.controller;
 
+import com.swyp.server.domain.user.dto.InviteCodeResponse;
 import com.swyp.server.domain.user.dto.ProfileRequest;
 import com.swyp.server.domain.user.dto.UserResponse;
 import com.swyp.server.domain.user.service.UserService;
@@ -47,4 +48,11 @@ public ResponseEntity<ApiResponse<Void>> agreeToTerms(@AuthenticationPrincipal L
         userService.agreeToTerms(userId);
         return ResponseEntity.ok(ApiResponse.success(null));
     }
+
+    @Operation(summary = "내 초대 코드 확인")
+    @GetMapping("me/invite-code")
+    public ResponseEntity<ApiResponse<InviteCodeResponse>> getInviteCode(
+            @AuthenticationPrincipal Long userId) {
+        return ResponseEntity.ok(ApiResponse.success(userService.getInviteCode(userId)));
+    }
 }

src/main/java/com/swyp/server/domain/user/dto/InviteCodeResponse.java

@@ -0,0 +1,9 @@
+package com.swyp.server.domain.user.dto;
+
+import com.swyp.server.domain.user.entity.User;
+
+public record InviteCodeResponse(String inviteCode) {
+    public static InviteCodeResponse from(User user) {
+        return new InviteCodeResponse(user.getInviteCode());
+    }
+}

src/main/java/com/swyp/server/domain/user/service/UserService.java

@@ -1,6 +1,7 @@
 package com.swyp.server.domain.user.service;
 
 import com.swyp.server.domain.auth.repository.RefreshTokenRepository;
+import com.swyp.server.domain.user.dto.InviteCodeResponse;
 import com.swyp.server.domain.user.dto.UserResponse;
 import com.swyp.server.domain.user.entity.Role;
 import com.swyp.server.domain.user.entity.User;
@@ -60,6 +61,19 @@ public UserResponse getMe(Long userId) {
         return UserResponse.from(user);
     }
 
+    @Transactional(readOnly = true)
+    public InviteCodeResponse getInviteCode(Long userId) {
+        User user =
+                userRepository
+                        .findById(userId)
+                        .orElseThrow(() -> new CustomException(ErrorCode.USER_NOT_FOUND));
+
+        if (!user.isProfileCompleted()) {
+            throw new CustomException(ErrorCode.PROFILE_NOT_COMPLETED);
+        }
+        return InviteCodeResponse.from(user);
+    }
+
     @Transactional
     public void updateProfile(Long userId, String nickname, UserType userType) {
         User user =

src/main/java/com/swyp/server/global/exception/ErrorCode.java

@@ -21,6 +21,7 @@ public enum ErrorCode {
     // User
     USER_NOT_FOUND(40401, 404, "사용자를 찾을 수 없습니다."),
     DUPLICATE_EMAIL(40901, 409, "이미 사용 중인 이메일입니다."),
+    PROFILE_NOT_COMPLETED(40026, 400, "프로필 설정 완료 후 이용할 수 있습니다."),
 
     // Todos
     TODO_NOT_FOUND(40402, 404, "할 일을 찾을 수 없습니다."),