bugfix - Make node schemas stricter

tests/integration_tests/extensions/nodes/giga_switch.py

@@ -1,5 +1,5 @@
 # © Crown-owned copyright 2025, Defence Science and Technology Laboratory UK
-from typing import Dict
+from typing import Dict, Literal
 
 from prettytable import MARKDOWN, PrettyTable
 
@@ -18,6 +18,9 @@ class GigaSwitch(NetworkNode, discriminator="gigaswitch"):
     :ivar num_ports: The number of ports on the switch. Default is 24.
     """
 
+    class ConfigSchema(NetworkNode.ConfigSchema):
+        type: Literal["gigaswitch"] = "gigaswitch"
+
     num_ports: int = 24
     "The number of ports on the switch."
     network_interfaces: Dict[str, SwitchPort] = {}