Add secure request/response helper

[GautamBytes]

Description

Proposed work

Add a generic request/response layer that:

• opens a fresh substream per request
• uses length-prefixed framing
• enforces bounded request/response sizes by default
• enforces a request timeout by default
• owns close/reset behavior internally
• supports pluggable codecs without forcing one serialization format

Public API

Add a new libp2p.request_response package exposing:

• RequestResponse
• RequestResponseConfig
• RequestContext
• RequestResponseCodec
• BytesCodec
• JSONCodec
• typed request/response exceptions

Initial scope

• one request
• one response
• one substream
• no retries
• no request IDs
• no streaming responses
• no protocol-specific or Filecoin-specific behavior

Validation goals

• unit tests for framing and codecs
• integration tests over real hosts
• example demonstrating a listener and dialer round trip
• docs for API and example usage

Acceptance criteria

• callers can register a handler for a protocol and send one request to a peer
• default limits and timeout are enforced
• malformed payloads and handler failures fail safely
• protocol negotiation failures are translated into typed helper errors
• docs and example are included

Motivation

Add a new libp2p.request_response helper that provides a safe, one-shot request/response API on top of libp2p streams.

Current Implementation

Today, applications that want a simple request/response pattern on top of py-libp2p have to build it manually on raw streams. That requires every caller to reimplement:

• framing
• timeouts
• payload size limits
• close vs reset behavior
• encode/decode error handling

This is easy to get wrong and leads to inconsistent security and reliability across applications.

Are you planning to do it yourself in a pull request ?

Yes