public void addIfValid(HeaderName headerName, String value) {
        Objects.requireNonNull(headerName, "headerName");
        Objects.requireNonNull(value, "value");
        if (isValid(headerName.getName()) && isValid(value)) {
            String normalName = headerName.getNormalised();
            addNormal(headerName.getName(), normalName, value);
        }
    }
Adds the name and value to the headers if valid
zuul-core/src/main/java/com/netflix/zuul/message/Headers.java