jodd-http/src/main/java/jodd/http/HeadersMultiMap.java
public void addHeader(final String name, final String value) {
		List<String> valuesList = super.getAll(name);
		if (valuesList.isEmpty()) {
			super.add(name, value);
			return;
		}
		super.remove(name);
		valuesList.add(value);
		super.addAll(name, valuesList);
	}
public void addHeader(final String name, final String value) {
		List<String> valuesList = super.getAll(name);
		if (valuesList.isEmpty()) {
			super.add(name, value);
			return;
		}
		super.remove(name);
		valuesList.add(value);
		super.addAll(name, valuesList);
	}
Adds new header value. If existing value exist, it will be removed
so the store the new key value.