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.

clientapi/routing/aliases.go

@@ -15,6 +15,7 @@
 package routing
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 
@@ -48,11 +49,12 @@ func GetAliases(
 	visibility := gomatrixserverlib.HistoryVisibilityInvited
 	if historyVisEvent, ok := stateRes.StateEvents[stateTuple]; ok {
 		var err error
-		visibility, err = historyVisEvent.HistoryVisibility()
-		if err != nil {
+		var content gomatrixserverlib.HistoryVisibilityContent
+		if err = json.Unmarshal(historyVisEvent.Content(), &content); err != nil {
 			util.GetLogger(req.Context()).WithError(err).Error("historyVisEvent.HistoryVisibility failed")
 			return util.ErrorResponse(fmt.Errorf("historyVisEvent.HistoryVisibility: %w", err))
 		}
+		visibility = content.HistoryVisibility
 	}
 	if visibility != spec.WorldReadable {
 		queryReq := api.QueryMembershipForUserRequest{

clientapi/routing/createroom.go

@@ -466,7 +466,7 @@ func createRoom(
 		}
 
 		// Add the event to the list of auth events
-		builtEvents = append(builtEvents, &types.HeaderedEvent{Event: ev})
+		builtEvents = append(builtEvents, &types.HeaderedEvent{PDU: ev})
 		err = authEvents.AddEvent(ev)
 		if err != nil {
 			util.GetLogger(ctx).WithError(err).Error("authEvents.AddEvent failed")
@@ -536,7 +536,7 @@ func createRoom(
 			case spec.MRoomMember:
 				fallthrough
 			case spec.MRoomJoinRules:
-				ev := event.Event
+				ev := event.PDU
 				globalStrippedState = append(
 					globalStrippedState,
 					fclient.NewInviteV2StrippedState(ev),
@@ -558,7 +558,7 @@ func createRoom(
 			}
 			inviteStrippedState := append(
 				globalStrippedState,
-				fclient.NewInviteV2StrippedState(inviteEvent.Event),
+				fclient.NewInviteV2StrippedState(inviteEvent.PDU),
 			)
 			// Send the invite event to the roomserver.
 			event := inviteEvent

clientapi/routing/directory.go

@@ -291,7 +291,7 @@ func SetVisibility(
 	}
 
 	// NOTSPEC: Check if the user's power is greater than power required to change m.room.canonical_alias event
-	power, _ := gomatrixserverlib.NewPowerLevelContentFromEvent(queryEventsRes.StateEvents[0].Event)
+	power, _ := gomatrixserverlib.NewPowerLevelContentFromEvent(queryEventsRes.StateEvents[0].PDU)
 	if power.UserLevel(dev.UserID) < power.EventLevel(spec.MRoomCanonicalAlias, true) {
 		return util.JSONResponse{
 			Code: http.StatusForbidden,

clientapi/routing/sendevent.go

@@ -185,7 +185,7 @@ func SendEvent(
 		req.Context(), rsAPI,
 		api.KindNew,
 		[]*types.HeaderedEvent{
-			&types.HeaderedEvent{Event: e},
+			&types.HeaderedEvent{PDU: e},
 		},
 		device.UserDomain(),
 		domain,
@@ -259,7 +259,7 @@ func generateSendEvent(
 	cfg *config.ClientAPI,
 	rsAPI api.ClientRoomserverAPI,
 	evTime time.Time,
-) (*gomatrixserverlib.Event, *util.JSONResponse) {
+) (gomatrixserverlib.PDU, *util.JSONResponse) {
 	// parse the incoming http request
 	userID := device.UserID
 
@@ -313,12 +313,12 @@ func generateSendEvent(
 	}
 
 	// check to see if this user can perform this operation
-	stateEvents := make([]*gomatrixserverlib.Event, len(queryRes.StateEvents))
+	stateEvents := make([]gomatrixserverlib.PDU, len(queryRes.StateEvents))
 	for i := range queryRes.StateEvents {
-		stateEvents[i] = queryRes.StateEvents[i].Event
+		stateEvents[i] = queryRes.StateEvents[i].PDU
 	}
 	provider := gomatrixserverlib.NewAuthEvents(gomatrixserverlib.ToPDUs(stateEvents))
-	if err = gomatrixserverlib.Allowed(e.Event, &provider); err != nil {
+	if err = gomatrixserverlib.Allowed(e.PDU, &provider); err != nil {
 		return nil, &util.JSONResponse{
 			Code: http.StatusForbidden,
 			JSON: jsonerror.Forbidden(err.Error()), // TODO: Is this error string comprehensible to the client?
@@ -343,5 +343,5 @@ func generateSendEvent(
 		}
 	}
 
-	return e.Event, nil
+	return e.PDU, nil
 }

clientapi/routing/server_notices.go

@@ -228,7 +228,7 @@ func SendServerNotice(
 		ctx, rsAPI,
 		api.KindNew,
 		[]*types.HeaderedEvent{
-			&types.HeaderedEvent{Event: e},
+			&types.HeaderedEvent{PDU: e},
 		},
 		device.UserDomain(),
 		cfgClient.Matrix.ServerName,