chore(restructure): reorganize project layout

- Reorganize internal packages and overall project structure
- Update imports and wiring to match the new layout
- Separate HTTP parsing and streaming from the server package
- Separate middleware from the server package
- Separate session registry from the session package
- Move HTTP, HTTPS, and TCP servers to the transport package
- Session package no longer starts the TCP server directly
- Server package no longer starts HTTP/HTTPS servers on initialization
- Forwarder no longer handles accepting TCP requests
- Move session details to the types package
- HTTP/HTTPS initialization is now the responsibility of main

internal/transport/tcp.go

@@ -0,0 +1,66 @@
+package transport
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+
+	"golang.org/x/crypto/ssh"
+)
+
+type tcp struct {
+	port      uint16
+	forwarder forwarder
+}
+
+type forwarder interface {
+	CreateForwardedTCPIPPayload(origin net.Addr) []byte
+	OpenForwardedChannel(payload []byte) (ssh.Channel, <-chan *ssh.Request, error)
+	HandleConnection(dst io.ReadWriter, src ssh.Channel)
+}
+
+func NewTCPServer(port uint16, forwarder forwarder) Transport {
+	return &tcp{
+		port:      port,
+		forwarder: forwarder,
+	}
+}
+
+func (tt *tcp) Listen() (net.Listener, error) {
+	return net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", tt.port))
+}
+
+func (tt *tcp) Serve(listener net.Listener) error {
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			if errors.Is(err, net.ErrClosed) {
+				return nil
+			}
+			log.Printf("Error accepting connection: %v", err)
+			continue
+		}
+		go tt.handleTcp(conn)
+	}
+}
+
+func (tt *tcp) handleTcp(conn net.Conn) {
+	defer func() {
+		err := conn.Close()
+		if err != nil {
+			log.Printf("Failed to close connection: %v", err)
+		}
+	}()
+	payload := tt.forwarder.CreateForwardedTCPIPPayload(conn.RemoteAddr())
+	channel, reqs, err := tt.forwarder.OpenForwardedChannel(payload)
+	if err != nil {
+		log.Printf("Failed to open forwarded-tcpip channel: %v", err)
+
+		return
+	}
+
+	go ssh.DiscardRequests(reqs)
+	tt.forwarder.HandleConnection(conn, channel)
+}