fix: serialize dates as ISO strings instead of arrays

src/main/resources/application.yaml

@@ -2,6 +2,10 @@ server:
   port: 8080
 
 spring:
+  jackson:
+    serialization:
+      write-dates-as-timestamps: false
+    date-format: yyyy-MM-dd'T'HH:mm:ss
   servlet:
     multipart:
       max-file-size: 1MB