Initial release of the middleware.
This version automatically handles prefixing the url that is sent back to the client with the root path of the mount point.
All that is required is to configure the FastMCP server as if it would be mounted at root, and wrap the sse_app in MountFastMCP middleware and it will fix the client post endpoint url that is sent back to the client. No need to set the basepath, as it will use root_path from the request scope to properly rewrite the url in the way that asgi servers are expected to.