public static void writeConfig(final Config config, final OutputStream outputStream) throws IOException {
        final ObjectMapper mapper = YamlUtil.getVanillaObjectMapper();
        // wrap the AppConfig so that it sits at the right level
        mapper.writeValue(outputStream, config);

    }
Reads a YAML string that has already been through the drop wizard env var substitution.
stroom-config/stroom-config-app/src/main/java/stroom/config/app/StroomYamlUtil.java