config: Add class member and methods for signalling/checking shutdown status

config.py

@@ -117,8 +117,16 @@ class AbstractConfig(abc.ABC):
     identifier: str
 
     def __init__(self) -> None:
+        self.in_shutdown = False  # Is the application currently shutting down ?
         self.home = pathlib.Path.home()
 
+    def set_shutdown(self):
+        self.in_shutdown = True
+
+    @property
+    def shutting_down(self) -> bool:
+        return self.in_shutdown
+
     @property
     def app_dir_str(self) -> str:
         """Return a string version of app_dir."""