Add threaded session backend architecture with real SSH backend

src/session_backend_factory.h

@@ -0,0 +1,12 @@
+#ifndef ORBITHUB_SESSION_BACKEND_FACTORY_H
+#define ORBITHUB_SESSION_BACKEND_FACTORY_H
+
+#include "profile_repository.h"
+
+#include <memory>
+
+class SessionBackend;
+
+std::unique_ptr<SessionBackend> createSessionBackend(const Profile& profile);
+
+#endif