in src/main/java/org/apache/sling/extensions/mdc/internal/MDCInsertingFilter.java [187:208]
private void modified(Config config){
Set<String> headers = new HashSet<>(Arrays.asList(config.headers()));
headerNames.clear();
headerNames.addAll(headers);
Set<String> cookies = new HashSet<>(Arrays.asList(config.cookies()));
cookieNames.clear();
cookieNames.addAll(cookies);
Set<String> params = new HashSet<>(Arrays.asList(config.parameters()));
parameterNames.clear();
parameterNames.addAll(params);
List<String> keyList = new ArrayList<>();
keyList.addAll(headerNames);
keyList.addAll(cookieNames);
keyList.addAll(parameterNames);
keyList.addAll(Arrays.asList(DEFAULT_KEY_NAMES));
this.keyNames.clear();
this.keyNames.addAll(keyList);
}