JDK HttpClient Streamable HTTP support #311

Hi there, I just want to followup about is there any plan for supporting the non-mcp-spring version of the streamablehttp client? The mcp-spring version of the client in below PR tested well. But our service is using a old spring framework so it's the available to use this client. Thanks!

== copied from previous PR conversation =
@bugzyz thank you! We are targetting Spring Framework gen 6, unfortunately. However, in your circumstances, once we introduce the JDK HttpClient support for Streamable HTTP, you should be able to use that in combination with older Spring Framework-based code. That work is coming once we finalize the architectural changes covered here. And then you wouldn't need the mcp-spring module dependency. Hope this helps.

Originally posted by @chemicL in #292 (comment)