[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/user.go

@@ -1112,13 +1112,13 @@ func (a *App) sendUpdatedUserEvent(user model.User) {
 	a.SanitizeProfile(adminCopyOfUser, true)
 	adminMessage := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_USER_UPDATED, "", "", "", nil)
 	adminMessage.Add("user", &adminCopyOfUser)
-	adminMessage.Broadcast.ContainsSensitiveData = true
+	adminMessage.GetBroadcast().ContainsSensitiveData = true
 	a.Publish(adminMessage)
 
 	a.SanitizeProfile(&user, false)
 	message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_USER_UPDATED, "", "", "", nil)
 	message.Add("user", &user)
-	message.Broadcast.ContainsSanitizedData = true
+	message.GetBroadcast().ContainsSanitizedData = true
 	a.Publish(message)
 }