When we try to create a kie container with name "demo_container" through Business-central, I get an error saying that it's an `invalid name`. The validation was changed to allow some additional characters (more specifically the use of a GAV as container name), so the validation was changed to this: https://github.com/droolsjbpm/kie-wb-common/pull/485/files
Since underscore(_) character is allowed in GAV elements, I think it should be allowed in container name too.