[MM-19914] Fix data races in WebSocketEvent (#13039)

* Make WebSocketEvent type immutable

* Update code to use updated immutable WebSocketEvent type

* Export WebSocketEvent fields and mark them as deprecated

app/web_conn.go

@@ -185,7 +185,7 @@ func (c *WebConn) writePump() {
 						"websocket.slow: dropping message",
 						mlog.String("user_id", c.UserId),
 						mlog.String("type", msg.EventType()),
-						mlog.String("channel_id", evt.Broadcast.ChannelId),
+						mlog.String("channel_id", evt.GetBroadcast().ChannelId),
 					)
 					skipSend = true
 				}
@@ -194,9 +194,7 @@ func (c *WebConn) writePump() {
 			if !skipSend {
 				var msgBytes []byte
 				if evtOk {
-					cpyEvt := &model.WebSocketEvent{}
-					*cpyEvt = *evt
-					cpyEvt.Sequence = c.Sequence
+					cpyEvt := evt.SetSequence(c.Sequence)
 					msgBytes = []byte(cpyEvt.ToJson())
 					c.Sequence++
 				} else {
@@ -209,7 +207,7 @@ func (c *WebConn) writePump() {
 							"websocket.full",
 							mlog.String("user_id", c.UserId),
 							mlog.String("type", msg.EventType()),
-							mlog.String("channel_id", evt.Broadcast.ChannelId),
+							mlog.String("channel_id", evt.GetBroadcast().ChannelId),
 							mlog.Int("size", len(msg.ToJson())),
 						)
 					} else {
@@ -305,11 +303,11 @@ func (webCon *WebConn) shouldSendEventToGuest(msg *model.WebSocketEvent) bool {
 	var userId string
 	var canSee bool
 
-	switch msg.Event {
+	switch msg.EventType() {
 	case model.WEBSOCKET_EVENT_USER_UPDATED:
-		userId = msg.Data["user"].(*model.User).Id
+		userId = msg.GetData()["user"].(*model.User).Id
 	case model.WEBSOCKET_EVENT_NEW_USER:
-		userId = msg.Data["user_id"].(string)
+		userId = msg.GetData()["user_id"].(string)
 	default:
 		return true
 	}
@@ -332,7 +330,7 @@ func (webCon *WebConn) ShouldSendEvent(msg *model.WebSocketEvent) bool {
 	// If the event contains sanitized data, only send to users that don't have permission to
 	// see sensitive data. Prevents admin clients from receiving events with bad data
 	var hasReadPrivateDataPermission *bool
-	if msg.Broadcast.ContainsSanitizedData {
+	if msg.GetBroadcast().ContainsSanitizedData {
 		hasReadPrivateDataPermission = model.NewBool(webCon.App.RolesGrantPermission(webCon.GetSession().GetUserRoles(), model.PERMISSION_MANAGE_SYSTEM.Id))
 
 		if *hasReadPrivateDataPermission {
@@ -341,7 +339,7 @@ func (webCon *WebConn) ShouldSendEvent(msg *model.WebSocketEvent) bool {
 	}
 
 	// If the event contains sensitive data, only send to users with permission to see it
-	if msg.Broadcast.ContainsSensitiveData {
+	if msg.GetBroadcast().ContainsSensitiveData {
 		if hasReadPrivateDataPermission == nil {
 			hasReadPrivateDataPermission = model.NewBool(webCon.App.RolesGrantPermission(webCon.GetSession().GetUserRoles(), model.PERMISSION_MANAGE_SYSTEM.Id))
 		}
@@ -352,19 +350,19 @@ func (webCon *WebConn) ShouldSendEvent(msg *model.WebSocketEvent) bool {
 	}
 
 	// If the event is destined to a specific user
-	if len(msg.Broadcast.UserId) > 0 {
-		return webCon.UserId == msg.Broadcast.UserId
+	if len(msg.GetBroadcast().UserId) > 0 {
+		return webCon.UserId == msg.GetBroadcast().UserId
 	}
 
 	// if the user is omitted don't send the message
-	if len(msg.Broadcast.OmitUsers) > 0 {
-		if _, ok := msg.Broadcast.OmitUsers[webCon.UserId]; ok {
+	if len(msg.GetBroadcast().OmitUsers) > 0 {
+		if _, ok := msg.GetBroadcast().OmitUsers[webCon.UserId]; ok {
 			return false
 		}
 	}
 
 	// Only report events to users who are in the channel for the event
-	if len(msg.Broadcast.ChannelId) > 0 {
+	if len(msg.GetBroadcast().ChannelId) > 0 {
 		if model.GetMillis()-webCon.LastAllChannelMembersTime > WEBCONN_MEMBER_CACHE_TIME {
 			webCon.AllChannelMembers = nil
 			webCon.LastAllChannelMembersTime = 0
@@ -380,15 +378,15 @@ func (webCon *WebConn) ShouldSendEvent(msg *model.WebSocketEvent) bool {
 			webCon.LastAllChannelMembersTime = model.GetMillis()
 		}
 
-		if _, ok := webCon.AllChannelMembers[msg.Broadcast.ChannelId]; ok {
+		if _, ok := webCon.AllChannelMembers[msg.GetBroadcast().ChannelId]; ok {
 			return true
 		}
 		return false
 	}
 
 	// Only report events to users who are in the team for the event
-	if len(msg.Broadcast.TeamId) > 0 {
-		return webCon.IsMemberOfTeam(msg.Broadcast.TeamId)
+	if len(msg.GetBroadcast().TeamId) > 0 {
+		return webCon.IsMemberOfTeam(msg.GetBroadcast().TeamId)
 	}
 
 	if webCon.GetSession().Props[model.SESSION_PROP_IS_GUEST] == "true" {