common: accept legacy namespace in changefeed ID JSON (#4080)

[ti-chi-bot]

This is an automated cherry-pick of #4080

What problem does this PR solve?

Issue Number: close #4079

What is changed and how it works?

• Accept legacy namespace field when unmarshalling ChangeFeedDisplayName JSON (treat it as an alias of keyspace).
• Marshal ChangeFeedDisplayName with both keyspace and legacy namespace to keep metadata readable across versions.
• Add a unit test to cover both formats.

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

Manual test: N/A

Questions

Will it cause performance regression or break compatibility?

No. This only changes JSON encoding/decoding for changefeed display name metadata and improves cross-version compatibility.

Do you need to update user documentation, design documentation or monitoring documentation?

No.

Release note

Fix changefeed metadata compatibility when upgrading between TiCDC versions that used "namespace" vs "keyspace" in changefeed ID JSON.

Summary by CodeRabbit

• Improvements

  • Improved JSON compatibility for display names: serialized output now includes both legacy and current field names so older and newer consumers can read data without migration; deserialization accepts either field and prefers the current one when both exist.

• Tests

  • Added unit tests covering forward/backward compatibility and serialization behavior.

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

1. It must be LGTMed and approved by the reviewers firstly.
2. For pull requests to TiDB-x branches, it must have no failed tests.
3. AFTER it has lgtm and approved labels, please wait for the cherry-pick merging approval from triage owners.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[gemini-code-assist]

Warning

You have reached your daily quota limit. Please wait up to 24 hours and I will start processing your requests again!

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 7cf64193-4717-4403-ac23-ddc19d931661

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wlwilliamx

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [wlwilliamx]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[wlwilliamx]

/test all