public boolean contains(HeaderName headerName, String value) {
        String normalName = Objects.requireNonNull(headerName, "headerName").getNormalised();
        Objects.requireNonNull(value, "value");
        return containsNormal(normalName, value);
    }
Returns if there is a header entry that matches the given name and value.
zuul-core/src/main/java/com/netflix/zuul/message/Headers.java