## Summary
Introduce `ExtraBodyField` annotation to enable parameters that arrive
via extra_body in client SDKs but are accessible server-side with full
typing.
These parameters are documented in OpenAPI specs under
**`x-llama-stack-extra-body-params`** but excluded from generated SDK
signatures.
Add `shields` parameter to `create_openai_response` as the first
implementation using this pattern.
## Test Plan
- added an integration test which checks that shields parameter passed
via extra_body reaches server implementation
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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Co-authored-by: Claude <noreply@anthropic.com>
