public boolean contains(String headerName, String value) {
        String normalName = HeaderName.normalize(Objects.requireNonNull(headerName, "headerName"));
        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