HDDS-5041. Use getShortUserName in getTrashRoot(s)

[smengcl]

https://issues.apache.org/jira/browse/HDDS-5041

Note: this commit changes the username set inside OFS .Trash directory when Kerberos is enabled from principal name to mapped shorted user name.

[xiaoyuyao]

Thanks @smengcl for working on this. The change LGTM. I just have one question: how do we handle the existing Trash location with full principal name? If it is not safe to do a rename, we should document how to migration after the change.

[smengcl]

Thanks @smengcl for working on this. The change LGTM. I just have one question: how do we handle the existing Trash location with full principal name? If it is not safe to do a rename, we should document how to migration after the change.

The existing Trash becomes inactive with the patch because the path has changed. I will document this in the markdown.

It's also a bit unfortunate that the full principal (typically has / in the name, testuser/scm@EXAMPLE.COM for example) creates two levels of user directory in .Trash. Though functionally it works just fine:

2021-05-21 18:20:00,170 [main] INFO fs.TrashPolicyDefault: Moved: 'ofs://om/vol2/buck2/README.md' to trash at: ofs://om/vol2/buck2/.Trash/testuser/scm@EXAMPLE.COM/Current/vol2/buck2/README.md

On a side note, the fundamental idea of this patch is the same as HDDS-5019. We are allowing user1/NODE1@EXAMPLE.COM and user2/NODE2@EXAMPLE.COM to be mapped to the same short user name, typically user1 in this case but configurable via hadoop.security.auth_to_local, when using the FileSystem (Trash in this case).

[xiaoyuyao]

Thanks @smengcl for the contribution. The change LGTM, +1.