private void copyResponseMap() {
        if (!modifiedDefaultResponseHeaders) {
            TreeSet<String> resCopy = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
            resCopy.addAll(suppressedResponseHeaders);
            modifiedDefaultResponseHeaders = true;
            this.suppressedResponseHeaders = resCopy;
        }
    }
No suppressed request nor response headers.
gateway/engine/core/src/main/java/io/apiman/gateway/engine/impl/AbstractConnectorConfig.java