ENH: fail for multiple requests (fail fast for unsupported requests)

src/main/java/org/caosdb/server/entity/Entity.java

@@ -700,7 +700,6 @@ public class Entity extends AbstractObservable implements EntityInterface {
     if (!this.isParsed) {
       this.isParsed = true;
       setValue(getDatatype().parseValue(getValue()));
-      this.isParsed = true;
     }
   }
 

src/main/java/org/caosdb/server/grpc/EntityTransactionServiceImpl.java

@@ -70,6 +70,9 @@ public class EntityTransactionServiceImpl extends EntityTransactionServiceImplBa
       if (sub_request.getRetrieveRequest().hasQuery() // Retrieves are either queries...
           && !sub_request.getRetrieveRequest().getQuery().getQuery().isBlank()) {
         final String query = sub_request.getRetrieveRequest().getQuery().getQuery();
+        if (container.getFlags().containsKey("query")) { // Check for more than one query request.
+          throw new CaosDBException("Cannot process more than one query request.");
+        }
         container.getFlags().put("query", query);
         if (isFileDownload) {
           container.getFlags().put("download_files", "true");