Stage 4: Keep-Alive & Pipelining

Real connections don't carry one request. With keep-alive, a client sends several requests down one socket — sometimes back-to-back before you've answered the first (pipelining). Your server must split the byte stream into requests using Content-Length, answer each in order, and know when to hang up.

Implement handleConnection(buffer, handler):

• buffer may contain multiple requests back-to-back; each request's body length comes from its Content-Length header (0 if absent)
• call handler(rawRequest) for each complete request, in order, and collect the returned response strings
• connection rules (HTTP/1.1): keep going by default; stop after a request with Connection: close (case-insensitive) — later bytes are ignored
• return { responses, close } where close is true if you stopped early