abstract command handlers away from proxy server

src/ProxyCommands.hh

@@ -0,0 +1,18 @@
+#pragma once
+
+#include <stdint.h>
+
+#include <string>
+
+#include "ServerState.hh"
+#include "ProxyServer.hh"
+
+
+
+void process_proxy_command(
+    std::shared_ptr<ServerState> s,
+    ProxyServer::LinkedSession& session,
+    bool from_server,
+    uint16_t command,
+    uint32_t flag,
+    std::string& data);