fix(api): 이메일 인증 중복 발생 시 오류 수정

src/main/java/com/onebyone/kindergarten/domain/user/entity/EmailCertification.java

@@ -32,4 +32,12 @@ public void completeCertification() {
     this.isCertificated = true;
     this.updatedAt = LocalDateTime.now();
   }
+
+  public void updateCode(String code) {
+    this.code = code;
+  }
+
+  public void markUncertificated() {
+    this.isCertificated = false;
+  }
 }

src/main/java/com/onebyone/kindergarten/domain/user/repository/EmailCertificationRepository.java

@@ -11,4 +11,7 @@ EmailCertification findByEmailAndCodeAndTypeAndDeletedAtIsNull(
       String email, String code, EmailCertificationType type);
 
   boolean existsByEmail(String email);
+
+  EmailCertification findByEmailAndType(
+      String email, EmailCertificationType emailCertificationType);
 }

src/main/java/com/onebyone/kindergarten/domain/user/service/UserService.java

@@ -338,43 +338,57 @@ public User signUpByApple(AppleUserResponse userResponse) {
     return user;
   }
 
-  @Transactional
-  public void updateHomeShortcut(Long userId, HomeShortcutsDto homeShortcutsDto) {
-    User user = getUserById(userId);
-    user.updateHomeShortcut(homeShortcutsDto.toJson());
-  }
-
   @Transactional
   public void saveSignUpCertification(EmailCertificationRequestDTO request, String certification) {
-    if (userRepository.existsByEmail(request.getEmail())) {
+    String email = request.getEmail();
+
+    if (userRepository.existsByEmail(email)) {
       throw new BusinessException(ErrorCodes.ALREADY_EXIST_EMAIL);
     }
 
     EmailCertification emailCert =
-        EmailCertification.builder()
-            .email(request.getEmail())
-            .type(EmailCertificationType.EMAIL)
-            .code(certification)
-            .isCertificated(false)
-            .build();
+        emailCertificationRepository.findByEmailAndType(email, EmailCertificationType.EMAIL);
+
+    if (emailCert == null) {
+      emailCert =
+          EmailCertification.builder().email(email).type(EmailCertificationType.EMAIL).build();
+    }
+
+    emailCert.updateCode(certification);
+    emailCert.markUncertificated();
 
     emailCertificationRepository.save(emailCert);
   }
 
+  @Transactional
+  public void updateHomeShortcut(Long userId, HomeShortcutsDto homeShortcutsDto) {
+    User user = getUserById(userId);
+    user.updateHomeShortcut(homeShortcutsDto.toJson());
+  }
+
   @Transactional
   public void savePasswordCertification(
       EmailCertificationRequestDTO request, String certification) {
+    String email = request.getEmail();
+
     if (!userRepository.existsByEmail(request.getEmail())) {
       throw new BusinessException(ErrorCodes.NOT_FOUND_USER);
     }
 
     EmailCertification passwordCert =
-        EmailCertification.builder()
-            .email(request.getEmail())
-            .type(EmailCertificationType.TEMPORARY_PASSWORD)
-            .code(certification)
-            .isCertificated(false)
-            .build();
+        emailCertificationRepository.findByEmailAndType(
+            email, EmailCertificationType.TEMPORARY_PASSWORD);
+
+    if (passwordCert == null) {
+      passwordCert =
+          EmailCertification.builder()
+              .email(email)
+              .type(EmailCertificationType.TEMPORARY_PASSWORD)
+              .build();
+    }
+
+    passwordCert.updateCode(certification);
+    passwordCert.markUncertificated();
 
     emailCertificationRepository.save(passwordCert);
   }