Add property 'id' to get service principal id

Author: pritishpai

src/databricks/labs/pytester/fixtures/iam.py

@@ -240,6 +240,11 @@ def application_id(self) -> str:
         assert self._service_principal.application_id is not None
         return self._service_principal.application_id
 
+    @property
+    def id(self) -> str:
+        assert self._service_principal.id is not None
+        return self._service_principal.id
+
     def __repr__(self):
         return f'RunAs({self.display_name})'