Using the proper exception

src/main/java/org/gcube/informationsystem/resourceregistry/instances/model/entities/EntityManagement.java

@@ -250,7 +250,7 @@ public abstract class EntityManagement<E extends Entity, ET extends EntityType>
 				String error = String.format(
 						"Trying to create an instance of %s of type %s which is abstract. The operation will be aborted.",
 						accessType.getName(), typeName);
-				throw new ResourceRegistryException(error);
+				throw new SchemaViolationException(error);
 			}
 			
 			OVertex vertexEntity = oDatabaseDocument.newVertex(typeName);