Implement forgetting about rooms (#1572)

* Add basic storage methods

* Add internal api handler

* Add check for forgotten room

* Add /rooms/{roomID}/forget endpoint

* Add missing rsAPI method

* Remove unused parameters

* Add passing tests

Signed-off-by: Till Faelligen <tfaelligen@gmail.com>

* Add missing file

* Add postgres migration

* Add sqlite migration

* Use Forgetter to forget room

* Remove empty line

* Update HTTP status codes

It looks like the spec calls for these to be 400, rather than 403: https://matrix.org/docs/spec/client_server/r0.6.1#post-matrix-client-r0-rooms-roomid-forget

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

roomserver/api/api_trace.go

@@ -194,6 +194,16 @@ func (t *RoomserverInternalAPITrace) PerformBackfill(
 	return err
 }
 
+func (t *RoomserverInternalAPITrace) PerformForget(
+	ctx context.Context,
+	req *PerformForgetRequest,
+	res *PerformForgetResponse,
+) error {
+	err := t.Impl.PerformForget(ctx, req, res)
+	util.GetLogger(ctx).WithError(err).Infof("PerformForget req=%+v res=%+v", js(req), js(res))
+	return err
+}
+
 func (t *RoomserverInternalAPITrace) QueryRoomVersionCapabilities(
 	ctx context.Context,
 	req *QueryRoomVersionCapabilitiesRequest,