fix: Refactor NettyServerConfig to use MessageCodecFactory directly

[xerial]

Summary

• Change NettyServerConfig to store MessageCodecFactory instead of PartialFunction
• Add codecFactory getter that ensures withMapOutput is applied for JSON serialization
• Update NettyResponseHandler to accept MessageCodecFactory directly
• Centralize codec factory creation to avoid duplication between response handler and request dispatcher

This follows the suggestion from Gemini code review on #4132 to pass MessageCodecFactory directly instead of PartialFunction, improving maintainability by making the codec dependency more explicit.

Test plan

• Compile netty module
• CI tests pass

🤖 Generated with Claude Code

[gemini-code-assist]

Summary of Changes

Hello @xerial, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the NettyServerConfig and NettyResponseHandler components to streamline how message codecs are managed and applied. By directly using MessageCodecFactory instead of PartialFunction, the changes make the codec dependencies more explicit and centralize their configuration, enhancing maintainability and reducing code duplication in the Netty HTTP server setup.

Highlights

• Configuration Refactoring: NettyServerConfig now directly stores a MessageCodecFactory instead of a PartialFunction, making codec dependencies more explicit.
• Centralized Codec Factory Access: A new codecFactory getter has been added to NettyServerConfig, ensuring that withMapOutput is consistently applied for JSON serialization.
• Simplified Response Handling: NettyResponseHandler has been updated to directly accept a MessageCodecFactory, removing internal codec factory creation logic.
• Reduced Duplication: Codec factory creation is now centralized, eliminating redundant logic between the response handler and request dispatcher.

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[gemini-code-assist]

Code Review

This pull request refactors NettyServerConfig to use MessageCodecFactory directly, improving maintainability by making the codec dependency more explicit and centralizing its creation. The changes are well-aligned with this goal and represent a good improvement to the codebase. I have one suggestion to simplify one of the new methods for better clarity and consistency.

[gemini-code-assist]

The implementation of this withCustomCodec overload can be simplified by calling customCodecFactory.withCodecs(m) directly, similar to the other overload for PartialFunction. This avoids the indirection of calling the other withCustomCodec overload and creating a verbose and slightly inefficient anonymous PartialFunction. It also makes the two overloads more parallel in their implementation.

  def withCustomCodec(m: Map[Surface, MessageCodec[_]]): NettyServerConfig = {
    this.copy(customCodecFactory = customCodecFactory.withCodecs(m))
  }