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

If value is {@code null}, then not added, but any existing header of same name is removed.

@throws ZuulException on invalid name or value
zuul-core/src/main/java/com/netflix/zuul/message/Headers.java