Sliding Sync: Add receipts extension (MSC3960) (#17489)

[MSC3960](https://github.com/matrix-org/matrix-spec-proposals/pull/3960): Receipts extension

Based on
[MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575):
Sliding Sync

1 files changed, 6 insertions, 0 deletions

diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py

index ccfce6bd53..c607d08de5 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -1150,6 +1150,12 @@ class SlidingSyncRestServlet(RestServlet):
                 },
             }
 
+        if extensions.receipts is not None:
+            serialized_extensions["receipts"] = {
+                # Same as the the top-level `account_data.events` field in Sync v2.
+                "rooms": extensions.receipts.room_id_to_receipt_map,
+            }
+
         return serialized_extensions