fix : null values in arrays were wrongly persisted as empty strings

src/main/java/fr/insee/genesis/domain/ports/api/LunaticJsonRawDataApiPort.java

@@ -27,7 +27,6 @@ public interface LunaticJsonRawDataApiPort {
     Set<String> findDistinctQuestionnaireIds();
     long countResponsesByQuestionnaireId(String campaignId);
     Page<LunaticJsonRawDataModel> findRawDataByCampaignIdAndDate(String campaignId, Instant  startDt, Instant endDt, Pageable pageable);
-
     DataProcessResult processRawData(String campaignName, List<String> interrogationIdList, List<GenesisError> errors) throws GenesisException;
     Map<String, List<String>> findProcessedIdsgroupedByQuestionnaireSince(LocalDateTime since);
 }

src/main/java/fr/insee/genesis/domain/service/rawdata/LunaticJsonRawDataService.java

@@ -405,7 +405,9 @@ private static void convertListVar(Object valuesForState, Map.Entry<String, Obje
         if (!values.isEmpty()) {
             int iteration = 1;
             for (String value : values) {
-                convertOneVar(collectedVariable, value, variablesMap, iteration, dstSurveyUnitModel);
+                if (value!=null) {
+                    convertOneVar(collectedVariable, value, variablesMap, iteration, dstSurveyUnitModel);
+                }
                 iteration++;
             }
         }

src/main/java/fr/insee/genesis/domain/utils/JsonUtils.java

@@ -28,7 +28,7 @@ public static Map<String, Object> asMap(Object obj) {
     public static List<String> asStringList(Object obj) {
         if (obj instanceof List<?> list) {
             return list.stream()
-                    .map(e -> e == null ? "" : String.valueOf(e))
+                    .map(e -> e == null ? null : String.valueOf(e))
                     .toList();
         }
         throw new IllegalArgumentException("Object is not a List");

src/test/java/fr/insee/genesis/domain/utils/JsonUtilsTest.java

@@ -65,7 +65,7 @@ void asStringList_shouldConvertValidList() {
         log.info("test");
         List<String> result = JsonUtils.asStringList(obj);
 
-        Assertions.assertThat(result).containsExactly("1", "text", "");
+        Assertions.assertThat(result).containsExactly("1", "text", null);
     }
 
     @Test