updates for zmanagement x3

src/main/java/org/zaine/app/service/CalendarSyncService.java

@@ -36,7 +36,9 @@ import java.time.temporal.Temporal;
 import java.util.ArrayList;
 import java.util.Base64;
 import java.util.Comparator;
+import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -157,11 +159,22 @@ public class CalendarSyncService {
             }
         }
 
-        return events.stream()
+        return deduplicate(events.stream()
                 .filter(event -> event.getStartsAt().isBefore(to.toOffsetDateTime())
                         && event.getEndsAt().isAfter(from.toOffsetDateTime()))
                 .sorted(Comparator.comparing(CalendarEvent::getStartsAt))
-                .toList();
+                .toList());
+    }
+
+    private List<CalendarEvent> deduplicate(List<CalendarEvent> events) {
+        Map<String, CalendarEvent> uniqueEvents = new LinkedHashMap<>();
+        for (CalendarEvent event : events) {
+            CalendarEvent duplicate = uniqueEvents.putIfAbsent(event.getExternalId(), event);
+            if (duplicate != null) {
+                logger.info("Skipping duplicate calendar event from " + event.getSource() + " at " + event.getStartsAt());
+            }
+        }
+        return List.copyOf(uniqueEvents.values());
     }
 
     private List<CalendarEvent> toCalendarEvents(