added a service category enum for readability

inventory_provider/tasks/worker.py

+import enum
 import json
 import logging
 import os
@@ -654,14 +655,19 @@ def refresh_finalizer(self, pending_task_ids_json):
     self.log_info('latched current/next dbs')
 
 
+class PollerServiceCategory(str, enum.Enum):
+    MDVPN = 'mdvpn'
+    LHCONE = 'lhcone'
+
+
 @log_task_entry_and_exit
 def _build_service_category_interface_list(update_callback=lambda s: None):
 
     def _classify(ifc):
         if ifc['description'].startswith('SRV_MDVPN'):
-            yield 'mdvpn'
+            yield PollerServiceCategory.MDVPN
         if 'LHCONE' in ifc['description']:
-            yield 'lhcone'
+            yield PollerServiceCategory.LHCONE
 
     update_callback('loading all known interfaces')
     interfaces = data.build_service_interface_user_list(InventoryTask.config)
@@ -673,9 +679,9 @@ def _build_service_category_interface_list(update_callback=lambda s: None):
     rp = r.pipeline()
 
     for ifc in interfaces:
-        for service_type in _classify(ifc):
+        for service_category in _classify(ifc):
             rp.set(
-                f'interface-services:{service_type}'
+                f'interface-services:{service_category.value}'
                 f':{ifc["router"]}:{ifc["interface"]}',
                 json.dumps(ifc))