m.room.redaction
events currently have an event-level property redacts which gives the event
ID of the event being redacted.
The presence of this field at the event level, rather than under the content
key, is anomalous. This MSC proposes that, in a future room version, the
redacts property be moved under the content key.
For backwards-compatibility with older clients, servers should add a redacts
property to the top level of m.room.redaction events in newer room versions
when serving such events over the Client-Server API.
For improved compatibility with newer clients, servers should add a redacts
property to the content of m.room.redaction events in older room versions
when serving such events over the Client-Server API.