docs(events): add note to ‹pre_check› default

Signed-off-by: Matej Focko <[email protected]>

packit_service/events/event.py

@@ -241,6 +241,9 @@ def pre_check(self) -> bool:
         Returns:
             `False` when we can ignore the event, `True` otherwise (for handling).
         """
+        # [SAFETY] Since majority of processed events do not require any
+        # validation, e.g., results from Copr/Koji, we default to the `True`
+        # here.
         return True
 
     @abstractmethod