feat: client-extensions

[EItanya]

Add extensions to the client macros

Motivation and Context

I am developing a client and I need to be able to pass extensions through my requests.

How Has This Been Tested?

Breaking Changes

This breaks the current macro code. I tried thinking of a way to do it without breaking, but I couldn't come up with any good ideas. Maybe a request builder where we can call with_extensions. Open to ideas here.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[salman1993]

what are extensions supposed to be in this case? i couldn't find any reference to extensions in MCP spec.

[4t145]

Sorry for late response. My opinion is to keep the basic api simple. If extension is a parameter here, why not other options like timeout or other things else. Maybe we could add extensions by calling send_request, or we could add a helper method to help to specific response type. Maybe we can have a trait to convert different request into json rpc resquest and give it response type.