CAMEL-23425: camel-openai - Add reasoning_content support and generic response header extraction

[Croway]

Summary

• Extract reasoning_content from API responses into a CamelOpenAIReasoningContent header, supporting thinking models like Qwen3 and DeepSeek-R1
• Add generic additionalResponseHeader option to map any extra response field to a named Camel header (e.g. additionalResponseHeader.reasoning_content=MyHeader)
• Both simple and agentic (MCP tool loop) non-streaming paths are covered

Test plan

• reasoning_content extracted into built-in header when present
• Empty content body preserved when only reasoning_content is present
• No header set when reasoning_content is absent
• Both inline <think> (CamelOpenAIThinkingContent) and reasoning_content headers populated independently
• additionalResponseHeader maps field to custom header name
• Custom header not set when field is absent
• All existing tests pass (mvn verify — 10 unit + 18 integration tests green)

Claude Code on behalf of Federico Mariani

[github-actions]

🌟 Thank you for your contribution to the Apache Camel project! 🌟
🤖 CI automation will test this PR automatically.

🐫 Apache Camel Committers, please review the following items:

• First-time contributors require MANUAL approval for the GitHub Actions to run
• You can use the command /component-test (camel-)component-name1 (camel-)component-name2.. to request a test from the test bot although they are normally detected and executed by CI.
• You can label PRs using skip-tests and test-dependents to fine-tune the checks executed by this PR.
• Build and test logs are available in the summary page. Only Apache Camel committers have access to the summary.

⚠️ Be careful when sharing logs. Review their contents before sharing them publicly.

[github-actions]

🧪 CI tested the following changed modules:

• catalog/camel-catalog
• components/camel-ai/camel-openai
• dsl/camel-endpointdsl
• test-infra/camel-test-infra-openai-mock

⚠️ Some tests are disabled on GitHub Actions (@DisabledIfSystemProperty(named = "ci.env.name")) and require manual verification:

• components/camel-ai/camel-openai: 6 test(s) disabled on GitHub Actions

All tested modules (14 modules)

• Camel :: AI :: LangChain4j :: Agent
• Camel :: AI :: LangChain4j :: Tools
• Camel :: AI :: OpenAI
• Camel :: Catalog :: Camel Catalog
• Camel :: Endpoint DSL
• Camel :: JBang :: MCP
• Camel :: JBang :: Plugin :: Route Parser
• Camel :: JBang :: Plugin :: TUI
• Camel :: JBang :: Plugin :: Validate
• Camel :: Launcher :: Container
• Camel :: Test Infra :: All test services
• Camel :: Test Infra :: OpenAI Mock
• Camel :: YAML DSL :: Validator
• Camel :: YAML DSL :: Validator Maven Plugin

---

⚙️ View full build and test results