#15391 fix REST API to expect a true/false string in isPreparation

src/main/java/de/thm/arsnova/services/IQuestionService.java

@@ -140,7 +140,7 @@ public interface IQuestionService {
     
     String getSubjectSortType(String sessionkey, String isPreparation);
     
-    SortOrder setSort(String sessionkey, String subject, String sortType, String questionVariant, String[] sortOrder);
+    SortOrder setSort(String sessionkey, String subject, String sortType, String isPreparation, String[] sortOrder);
     
     String getQuestionSortType(String sessionkey, String isPreparation, String subject);
 }

src/main/java/de/thm/arsnova/services/QuestionService.java

@@ -794,8 +794,12 @@ public class QuestionService implements IQuestionService, ApplicationEventPublis
     }
     
     @Override 
-    public SortOrder setSort(String sessionkey, String subject, String sortType, String questionVariant, String[] sortOrderList) {
+    public SortOrder setSort(String sessionkey, String subject, String sortType, String isPreparation, String[] sortOrderList) {
         Session session = databaseDao.getSessionFromKeyword(sessionkey);
+		String questionVariant = "preparation";
+		if ("false".equals(isPreparation)) {
+			questionVariant = "lecture";
+		}
         SortOrder existing = databaseDao.getSortOrder(session.get_id(), questionVariant, subject);
         SortOrder sortOrder = new SortOrder();
         if (existing != null) {