refactor(analytocs): obfuscate android id

#1863

Author: jo-elimu

src/main/java/ai/elimu/model/analytics/LearningEvent.java

@@ -51,7 +51,12 @@ public void setTimestamp(Calendar timestamp) {
     }
 
     public String getAndroidId() {
-        return androidId;
+        if (!androidId.contains("***")) {
+            // Hide parts of the Android ID, e.g. "7161a85a0e4751cd" --> "7161***51cd"
+            return androidId.substring(0, 4) + "***" + androidId.substring(12);
+        } else {
+            return androidId;
+        }
     }
 
     public void setAndroidId(String androidId) {

src/main/java/ai/elimu/web/analytics/StoryBookLearningEventCsvExportController.java

@@ -65,6 +65,7 @@ public void handleRequest(
             );
 
             csvPrinter.flush();
+            csvPrinter.close();
         }
 
         String csvFileContent = stringWriter.toString();