add example to generate dm key

[D3Hunter]

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[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-11-04 06:08:04.146198325 +0000 UTC m=+848396.985353872: :ballot_box_with_check: agreed by lance6716.

[ti-chi-bot[bot]]

@joccau: adding LGTM is restricted to approvers and reviewers in OWNERS files.

In response to [this](https://github.com/pingcap/docs/pull/19306#pullrequestreview-2412227669): >LGTM Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[qiancai]

/approve

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #19345.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.4: #19346.