Try and drop stale extremities. (#8929)

If we see stale extremities while persisting events, and notice that
they don't change the result of state resolution, we drop them.

1 files changed, 2 insertions, 0 deletions

diff --git a/synapse/api/constants.py b/synapse/api/constants.py

index 1932df83b4..565a8cd76a 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -95,6 +95,8 @@ class EventTypes:
 
     Presence = "m.presence"
 
+    Dummy = "org.matrix.dummy_event"
+
 
 class RejectedReason:
     AUTH_ERROR = "auth_error"