Implement MSC3952: Intentional mentions (#14823)

MSC3952 defines push rules which searches for mentions in a list of
Matrix IDs in the event body, instead of searching the entire event
body for display name / local part.

This is implemented behind an experimental configuration flag and
does not yet implement the backwards compatibility pieces of the MSC.

1 files changed, 3 insertions, 0 deletions

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

index 6f9239d21c..0f224b34cd 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -233,6 +233,9 @@ class EventContentFields:
     # The authorising user for joining a restricted room.
     AUTHORISING_USER: Final = "join_authorised_via_users_server"
 
+    # Use for mentioning users.
+    MSC3952_MENTIONS: Final = "org.matrix.msc3952.mentions"
+
     # an unspecced field added to to-device messages to identify them uniquely-ish
     TO_DEVICE_MSGID: Final = "org.matrix.msgid"