Indicate deleteBy in post_deleted websocket event (#15332)

This lets the client know who deleted the post. This information is
stored in the database, but cannot be retrieved from an API endpoint
because the API does not return information about deleted post.

Currently, the information is only sent to system administrators.

app/post.go

@@ -1041,9 +1041,18 @@ func (a *App) DeletePost(postId, deleteByID string) (*model.Post, *model.AppErro
 		}
 	}
 
-	message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POST_DELETED, "", post.ChannelId, "", nil)
-	message.Add("post", a.PreparePostForClient(post, false, false).ToJson())
-	a.Publish(message)
+	postData := a.PreparePostForClient(post, false, false).ToJson()
+
+	userMessage := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POST_DELETED, "", post.ChannelId, "", nil)
+	userMessage.Add("post", postData)
+	userMessage.GetBroadcast().ContainsSanitizedData = true
+	a.Publish(userMessage)
+
+	adminMessage := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POST_DELETED, "", post.ChannelId, "", nil)
+	adminMessage.Add("post", postData)
+	adminMessage.Add("delete_by", deleteByID)
+	adminMessage.GetBroadcast().ContainsSensitiveData = true
+	a.Publish(adminMessage)
 
 	a.Srv().Go(func() {
 		a.DeletePostFiles(post)