public void addResponseProp(String key, String value) {
        if (responseProps == null) {
            responseProps = new HashMap<String, String>(16);
        }
        if (key != null && value != null) {
            responseProps.put(key, value);
        }
    }
Add response prop.

@param key   the key
@param value the value
core/api/src/main/java/com/alipay/sofa/rpc/core/response/SofaResponse.java