add-keys_test.go

[take0420]

Which problem is this PR solving?

Resolves ：#5129

Description of the changes

• Added 4 new unit tests in internal/metricstest/keys_test.go covering various scenarios for the GetKey function. These include:

1. A basic case with a single tag.
2. Multiple tags with sorting.
3. A case with no tags.
4. Multiple tags and special characters.

How was this change tested?

• Testing:
  The new tests have been executed locally, and all passed successfully. Here's the output for reference:

=== RUN   TestGetKey
--- PASS: TestGetKey (0.00s)
PASS
ok      command-line-arguments  0.281s

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: yarn lint and yarn test

Thank you for considering my pull request.

Best regards,

@take0420

[take0420]

This is my first time commitment 🙏🔰

https://goodfirstissue.dev/language/go

[Pushkarm029]

@take0420, DCO is failing because your 1st commit wasn't signed.please follow the instructions present here: https://github.com/jaegertracing/jaeger/pull/5249/checks?check_run_id=22299996926

[yurishkuro]

this looks just like a copy of #5249.