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