private void addContainerNetwork(RunImageConfiguration runConfig, List<String> ret) {
        NetworkConfig config = runConfig.getNetworkingConfig();
        String alias = config.getContainerAlias();
        if (alias != null) {
            ret.add(alias);
        }
    }
Override externalConfiguration when defined via special property.

@param externalConfiguration Map with alternative config
src/main/java/io/fabric8/maven/docker/config/ImageConfiguration.java