Add an ability to trace requests

Expected Behavior

User can specify a file to dump information about all requests being sent between MCP server and the client

Current Behavior

I don't think there is a way to do it currently.

Context

We created a LoggingServletTransportProvider which does that, but with the new changes that no longer compiles since there is no public constructor. Using the builder and then composing is also not possible because the methods are protected.

We could upstream the LoggingServletTransportProvider or something along these lines if it makes sense.

This is very useful for debugging potential issues with MCP servers especially when users turn on automatic accept.

まず、リンクされている Scala LoggingServletTransportProvider と、Java SDK の現在の builder および protected な transport メソッドを比較します。アクセスできないコンストラクターやメソッドに依存せずに、リクエストトレーシングでユーザーが選択した出力ファイルを公開する方法を判断します。ユーザーがファイルを設定し、MCP server と client の間で交換されたリクエストの情報を確認できれば完了です。