fix: prompt_cache_key openai chat -> openai responses

[seefs001]

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补充 chat转responses prompt_cache_key

🚀 变更类型 / Type of change

• 🐛 Bug 修复 (Bug fix) - 请关联对应 Issue，避免将设计取舍、理解偏差或预期不一致直接归类为 bug
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• ⚡ 性能优化 / 重构 (Refactor)
• 📝 文档更新 (Documentation)

🔗 关联任务 / Related Issue

• Related [Bug] Chat/Claude → OpenAI Responses 转换未透传 prompt_cache_key，导致缓存亲和失效 #6538

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Summary by CodeRabbit

• Bug Fixes

  • Preserved prompt cache keys when converting chat completion requests to responses requests.
  • Correctly handles escaped and Unicode prompt cache key values.
  • Omits the prompt cache key when no value is provided.

• Tests

  • Added coverage for prompt cache key preservation and JSON serialization.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 2d09f626-2e77-4114-9ef3-181e22a60dd6

📥 Commits

Reviewing files that changed from the base of the PR and between 47ba9d2 and c1838f7.

📒 Files selected for processing (2)

• relaykit/relayconvert/internal/oai_chat/to_oai_responses_req.go
• relaykit/relayconvert/internal/oai_chat/to_oai_responses_req_test.go

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Walkthrough

The request conversion now preserves non-empty PromptCacheKey values in OpenAIResponsesRequest. Tests cover escaped, Unicode, serialized, and unset values.

Changes

Prompt cache key conversion

Layer / File(s)	Summary
Convert and validate prompt cache keys relaykit/relayconvert/internal/oai_chat/to_oai_responses_req.go, relaykit/relayconvert/internal/oai_chat/to_oai_responses_req_test.go	The converter serializes and assigns non-empty PromptCacheKey values. Tests verify escaped and Unicode values, JSON serialization, and omission when unset.

Estimated code review effort: 2 (Simple) | ~5 minutes

Suggested reviewers: wans10

Poem

A rabbit hops through JSON bright,
Carrying cache keys left and right.
Escapes, Unicode, all pass through,
Empty keys fade from output too.
Conversion lands with tests in flight.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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