Add possibility to ignore users (#2329)

* Add ignore users

* Ignore users in pushrules
Add passing tests

* Update sytest lists

* Store ignore knowledge in the sync API

* Fix copyrights

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

syncapi/streams/stream_sendtodevice.go

@@ -48,6 +48,10 @@ func (p *SendToDeviceStreamProvider) IncrementalSync(
 
 		// Add the updates into the sync response.
 		for _, event := range events {
+			// skip ignored user events
+			if _, ok := req.IgnoredUsers.List[event.Sender]; ok {
+				continue
+			}
 			req.Response.ToDevice.Events = append(req.Response.ToDevice.Events, event.SendToDeviceEvent)
 		}
 	}