add support for changing task item.

api/task.go

@@ -86,6 +86,24 @@ func Task(g *gin.RouterGroup, db database.Database) {
 			return nil, err
 		}
 
+		if update.ItemID != nil && *update.ItemID != task.ItemID {
+			_, err := l.FindItem(c.Request.Context(), *update.ItemID)
+			if err != nil {
+				return nil, err
+			}
+
+			logs, err := l.ListLogs(c.Request.Context(), models.LogFilter{
+				TaskIDs: []string{task.ID},
+			})
+			if err != nil {
+				return nil, err
+			}
+
+			if len(logs) > 0 {
+				return nil, slerrors.Forbidden("You cannot change the item if the task has logs.")
+			}
+		}
+
 		task.Update(update)
 		if task.EndTime != nil && task.EndTime.Before(task.CreatedTime) {
 			return nil, slerrors.BadRequest("Task end time must be later than it was created.")