refactor: make the ITService class a singleton

RHCLOUD-29641

rbac/management/principal/it_service.py

@@ -73,6 +73,16 @@ def limit_offset_validation(offset, limit):
 class ITService:
     """A class to handle interactions with the IT service."""
 
+    # Instance variable for the class.
+    _instance = None
+
+    def __new__(cls, *args, **kwargs):
+        """Create a single instance of the class."""
+        if cls._instance is None:
+            cls._instance = super().__new__(cls, *args, **kwargs)
+
+        return cls._instance
+
     def __init__(self):
         """Establish IT connection information."""
         self.host = settings.IT_SERVICE_HOST

tests/management/principal/test_it_service.py

@@ -33,6 +33,23 @@ class ITServiceTests(IdentityRequest):
     def setUp(self):
         self.it_service = ITService()
 
+    def test_it_service_singleton(self):
+        """Test that the IT Service class only gets instantiated once."""
+        class_instances = [
+            ITService(),
+            ITService(),
+            ITService(),
+            ITService(),
+            ITService(),
+        ]
+
+        for instance in class_instances:
+            self.assertEqual(
+                self.it_service,
+                instance,
+                "no new instances of the IT service class should have been created since it is supposed to be a singleton",
+            )
+
     @mock.patch("management.principal.it_service.ITService._is_service_account_valid")
     def test_is_service_account_valid_by_username_client_id(self, _is_service_account_valid: mock.Mock):
         """Test that the function under test calls the underlying function with the unmodified client ID."""