回滚失败通知

遇到脏数据导致事务回滚失败，一直重试，怎么能做到邮件通知（或者应用怎么能监听到回滚失败），官方文档说实现FailureHandler，不是太理解。

Start with the official FailureHandler documentation referenced in the issue and trace how rollback failures caused by dirty data are surfaced. Determine whether the requested outcome is an email notification, an application listener, or clearer guidance, then document the supported behavior and a verifiable completion criterion.

Written by the indexing model from the issue text.