effectively disable type checking on ObjectEvent namespace (#982)

Co-authored-by: Ben Hoyt <ben.hoyt@canonical.com>

ops/framework.py

@@ -489,6 +489,14 @@ def __repr__(self):
         event_kinds = ', '.join(sorted(self._event_kinds()))
         return f'<{k.__module__}.{k.__qualname__}: {event_kinds}>'
 
+    def __getattr__(self, name: str) -> Any:
+        """The existence of this method tells type checkers to allow dynamic attributes.
+
+        This allows charms to access dynamically-defined events such as
+        ``self.on.db_relation_joined`` without Mypy/Pyright whining.
+        """
+        return super().__getattribute__(name)
+
 
 class PrefixedEvents:
     """Events to be found in all events using a specific prefix."""