Use PDU not *Event in HeaderedEvent (#3073)

Requires https://github.com/matrix-org/gomatrixserverlib/pull/376

This has numerous upsides:
 - Less type casting to `*Event` is required.
- Making Dendrite work with `PDU` interfaces means we can swap out Event
impls more easily.
 - Tests which represent weird event shapes are easier to write.

Part of a series of refactors on GMSL.

syncapi/consumers/roomserver.go

@@ -526,7 +526,7 @@ func (s *OutputRoomEventConsumer) updateStateEvent(event *rstypes.HeaderedEvent)
 		PrevSender:    prevEvent.Sender(),
 	}
 
-	event.Event, err = event.SetUnsigned(prev)
+	event.PDU, err = event.SetUnsigned(prev)
 	succeeded = true
 	return event, err
 }

syncapi/routing/relations.go

@@ -113,7 +113,7 @@ func Relations(
 	for _, event := range filteredEvents {
 		res.Chunk = append(
 			res.Chunk,
-			synctypes.ToClientEvent(event.Event, synctypes.FormatAll),
+			synctypes.ToClientEvent(event.PDU, synctypes.FormatAll),
 		)
 	}
 

syncapi/storage/shared/storage_consumer.go

@@ -352,13 +352,13 @@ func (d *Database) RedactEvent(ctx context.Context, redactedEventID string, reda
 		logrus.WithField("event_id", redactedEventID).WithField("redaction_event", redactedBecause.EventID()).Warnf("missing redacted event for redaction")
 		return nil
 	}
-	eventToRedact := redactedEvents[0].Event
-	redactionEvent := redactedBecause.Event
+	eventToRedact := redactedEvents[0].PDU
+	redactionEvent := redactedBecause.PDU
 	if err = eventutil.RedactEvent(redactionEvent, eventToRedact); err != nil {
 		return err
 	}
 
-	newEvent := &rstypes.HeaderedEvent{Event: eventToRedact}
+	newEvent := &rstypes.HeaderedEvent{PDU: eventToRedact}
 	err = d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
 		return d.OutputEvents.UpdateEventJSON(ctx, txn, newEvent)
 	})
@@ -493,7 +493,7 @@ func (d *Database) CleanSendToDeviceUpdates(
 
 // getMembershipFromEvent returns the value of content.membership iff the event is a state event
 // with type 'm.room.member' and state_key of userID. Otherwise, an empty string is returned.
-func getMembershipFromEvent(ev *gomatrixserverlib.Event, userID string) (string, string) {
+func getMembershipFromEvent(ev gomatrixserverlib.PDU, userID string) (string, string) {
 	if ev.Type() != "m.room.member" || !ev.StateKeyEquals(userID) {
 		return "", ""
 	}

syncapi/storage/shared/storage_sync.go

@@ -429,7 +429,7 @@ func (d *DatabaseTransaction) GetStateDeltas(
 		for _, ev := range stateStreamEvents {
 			// Look for our membership in the state events and skip over any
 			// membership events that are not related to us.
-			membership, prevMembership := getMembershipFromEvent(ev.Event, userID)
+			membership, prevMembership := getMembershipFromEvent(ev.PDU, userID)
 			if membership == "" {
 				continue
 			}
@@ -555,7 +555,7 @@ func (d *DatabaseTransaction) GetStateDeltasForFullStateSync(
 
 	for roomID, stateStreamEvents := range state {
 		for _, ev := range stateStreamEvents {
-			if membership, _ := getMembershipFromEvent(ev.Event, userID); membership != "" {
+			if membership, _ := getMembershipFromEvent(ev.PDU, userID); membership != "" {
 				if membership != spec.Join { // We've already added full state for all joined rooms above.
 					deltas[roomID] = types.StateDelta{
 						Membership:    membership,

syncapi/types/types.go

@@ -552,7 +552,7 @@ func NewInviteResponse(event *types.HeaderedEvent) *InviteResponse {
 
 	// Then we'll see if we can create a partial of the invite event itself.
 	// This is needed for clients to work out *who* sent the invite.
-	inviteEvent := synctypes.ToClientEvent(event.Event, synctypes.FormatSync)
+	inviteEvent := synctypes.ToClientEvent(event.PDU, synctypes.FormatSync)
 	inviteEvent.Unsigned = nil
 	if ev, err := json.Marshal(inviteEvent); err == nil {
 		res.InviteState.Events = append(res.InviteState.Events, ev)

syncapi/types/types_test.go

@@ -56,7 +56,7 @@ func TestNewInviteResponse(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	res := NewInviteResponse(&types.HeaderedEvent{Event: ev})
+	res := NewInviteResponse(&types.HeaderedEvent{PDU: ev})
 	j, err := json.Marshal(res)
 	if err != nil {
 		t.Fatal(err)