Updating log level when invalid route (#2616)

At the moment we are logging as DEBUG the fact that we are ignoring a new route and that the gateway will not have the expected status.

Even if the client will get the BAD_REQUEST, we should log the fact that we are ignoring this new route.

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/actuate/AbstractGatewayControllerEndpoint.java

@@ -160,7 +160,7 @@ public class AbstractGatewayControllerEndpoint implements ApplicationEventPublis
 
 	private void handleUnavailableDefinition(String simpleName, Set<String> unavailableDefinitions) {
 		final String errorMessage = String.format("Invalid %s: %s", simpleName, unavailableDefinitions);
-		log.debug(errorMessage);
+		log.warn(errorMessage);
 		throw new ResponseStatusException(HttpStatus.BAD_REQUEST, errorMessage);
 	}