Add ephemeral messages support (MSC2228) (#6409)

Implement part [MSC2228](https://github.com/matrix-org/matrix-doc/pull/2228). The parts that differ are:

* the feature is hidden behind a configuration flag (`enable_ephemeral_messages`)
* self-destruction doesn't happen for state events
* only implement support for the `m.self_destruct_after` field (not the `m.self_destruct` one)
* doesn't send synthetic redactions to clients because for this specific case we consider the clients to be able to destroy an event themselves, instead we just censor it (by pruning its JSON) in the database

1 files changed, 21 insertions, 0 deletions

diff --git a/synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql b/synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql
new file mode 100644
index 0000000000..81a36a8b1d
--- /dev/null
+++ b/synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql
@@ -0,0 +1,21 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+CREATE TABLE IF NOT EXISTS event_expiry (
+    event_id TEXT PRIMARY KEY,
+    expiry_ts BIGINT NOT NULL
+);
+
+CREATE INDEX event_expiry_expiry_ts_idx ON event_expiry(expiry_ts);