pitr: support s3 object lock (#16715)

br/backup-and-restore-storages.md

@@ -260,4 +260,10 @@ BR supports specifying the Azure server-side encryption scope or providing the e
 
 ## Other features supported by the storage service
 
-BR v6.3.0 supports AWS [S3 Object Lock](https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-lock.html). You can enable this feature to prevent backup data from being tampered with or deleted.
+Amazon [S3 Object Lock](https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-lock.html) can help prevent backup data from accidental or intentional deletion during a specified retention period, enhancing the security and integrity of data. Starting from v6.3.0, BR supports Amazon S3 Object Lock for snapshot backups, adding an additional layer of security for full backups. Starting from v8.0.0, PITR also supports Amazon S3 Object Lock. Whether for full backups or log data backups, the Object Lock feature ensures more reliable data protection, further strengthening the security of data backup and recovery and meeting regulatory requirements.
+
+BR and PITR automatically detect whether the Amazon S3 Object Lock feature is enabled or disabled. You do not need to perform any additional operations.
+
+> **Warning:**
+>
+> If the Object Lock feature is enabled during the snapshot backup or PITR log backup process, the snapshot backup or log backup might fail. You need to restart the snapshot backup or PITR log backup task to continue the backup.