Set uuid on Management instance to avoid null in logs during tests

src/main/java/org/gcube/informationsystem/resourceregistry/instances/base/ElementManagement.java

@@ -390,6 +390,7 @@ public abstract class ElementManagement<El extends OElement, T extends Type> {
 				element.setProperty(IdentifiableElement.HEADER_PROPERTY, entityHeader);
 			} else {
 				entityHeader = HeaderUtility.addHeader(element, null);
+				uuid = entityHeader.getUUID();
 			}
 			
 			getWorkingContext().addElement(element, oDatabaseDocument);