fix: enum type 소문자 직렬화로 변경

src/main/java/com/aolda/itda/entity/certificate/Challenge.java

 package com.aolda.itda.entity.certificate;
 
+import com.fasterxml.jackson.annotation.JsonFormat;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+@JsonFormat(shape = JsonFormat.Shape.STRING)
 public enum Challenge {
-    HTTP, DNS_CLOUDFLARE
+    HTTP, DNS_CLOUDFLARE;
+
+    @JsonValue
+    @Override
+    public String toString() {
+        return name().toLowerCase();
+    }
 }

src/main/java/com/aolda/itda/entity/log/Action.java

 package com.aolda.itda.entity.log;
 
+import com.fasterxml.jackson.annotation.JsonFormat;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+@JsonFormat(shape = JsonFormat.Shape.STRING)
 public enum Action {
-    CREATE, UPDATE, DELETE
+    CREATE, UPDATE, DELETE;
+
+    @JsonValue
+    @Override
+    public String toString() {
+        return name().toLowerCase();
+    }
 }

src/main/java/com/aolda/itda/entity/log/ObjectType.java

 package com.aolda.itda.entity.log;
 
+import com.fasterxml.jackson.annotation.JsonFormat;
+import com.fasterxml.jackson.annotation.JsonValue;
+
+@JsonFormat(shape = JsonFormat.Shape.STRING)
 public enum ObjectType {
-    ROUTING, CERTIFICATE, FORWARDING
+    ROUTING, CERTIFICATE, FORWARDING;
+
+    @JsonValue
+    @Override
+    public String toString() {
+        return name().toLowerCase();
+    }
 }