private ConfigChangeType getChangeType(String configInfo, String oldValue) {
            if (StringUtils.isBlank(configInfo)) {
                return ConfigChangeType.DELETED;
            }
            if (StringUtils.isBlank(oldValue)) {
                return ConfigChangeType.ADDED;
            }
            return ConfigChangeType.MODIFIED;
        }
receive config change event

@param dataId     data ID
@param group      group
@param configInfo content
config/config-nacos/src/main/java/com/alipay/sofa/rpc/dynamic/nacos/NacosDynamicConfigManager.java