private static ConfigDef config() {
            ConfigDef result = new ConfigDef().withClientSslSupport();
            addInternalConfig(result);
            return result;
        }
Add the properties related to an internal-only server to the given {@link ConfigDef}.
@param configDef the {@link ConfigDef} to add the properties to; may not be null
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/rest/RestServerConfig.java