Fix CLI and Session to work with new classes

src/primaite/utils/start_gate_server.py

@@ -1,5 +1,12 @@
 """Utility script to start the gate server for running PrimAITE in attached mode."""
 from arcd_gate.server.gate_service import GATEService
 
-service = GATEService()
-service.start()
+
+def start_gate_server():
+    """Start the gate server."""
+    service = GATEService()
+    service.start()
+
+
+if __name__ == "__main__":
+    start_gate_server()