public void set(HeaderName headerName, String value) {
        String normalName = Objects.requireNonNull(headerName, "headerName").getNormalised();
        setNormal(headerName.getName(), normalName, value);
    }
Replace any/all entries with this key, with this single entry.

If value is {@code null}, then not added, but any existing header of same name is removed.
zuul-core/src/main/java/com/netflix/zuul/message/Headers.java