@Override
        public Stream<ValidationEvent> visitEndpoint(Endpoint endpoint) {
            checkingEndpoint = true;
            Stream<ValidationEvent> errors = endpoint.getUrl().accept(this);
            checkingEndpoint = false;
            return errors;
        }
Validate that URIs start with a scheme.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/validators/RuleSetUriValidator.java