private static void loadExternalConfig() throws IOException {
        String configFile = System.getProperty("CONDUCTOR_CONFIG_FILE");
        if (StringUtils.isNotBlank(configFile)) {
            FileSystemResource resource = new FileSystemResource(configFile);
            if (resource.exists()) {
                Properties properties = new Properties();
                properties.load(resource.getInputStream());
                properties.forEach(
                        (key, value) -> System.setProperty((String) key, (String) value));
                log.info("Loaded {} properties from {}", properties.size(), configFile);
            } else {
                log.warn("Ignoring {} since it does not exist", configFile);
            }
        }
    }
Reads properties from the location specified in <code>CONDUCTOR_CONFIG_FILE</code> and sets
them as system properties so they override the default properties.

<p>Spring Boot property hierarchy is documented here,
https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-external-config

@throws IOException if file can't be read.
server/src/main/java/com/netflix/conductor/Conductor.java