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