Implement streamable HTTP transport with Redis-based session management

[jerome3o-anthropic]

This is me trying to add shttp to the example server deployment, it's multi instance so I need to relay mcp messages across redis

Context

SSE

This is how the SSE works in this repo

SHTTP

This server, for demonstration purposes, implements a stateful mcp server with shttp using redis and background tasks. it works like this:

When you initialize a session the container that handles the request starts up the MCP server (and runs it async), and wires it up to a transport that runs over redis.

Then for every request to that session we instantiate a streamable http transport object (to handle the http behaviour) and relay all MCP messages via the redis transport to the MCP server

it requires mcp messages being passed back and forward through redis, hence the redis MCP transport. I implemented many proxies like this for the claudeai MCP functionality, so I believe this shouldn't be an out-of-distribution task for the transports to implement.

I ran into a few issues:

• relaying the transports was tricky because we have extra and options on the send and onmessage functions making them asymmetrical (meaning chaining transports is non-trivial)
• the streamable http transport implementation assumes that it will be the only instance of the transport receiving the mcp messages, and raises when it gets a message that isn't for the current response it relates to