Is there a certain notification scheme or add-on I can use that will alert people when a dependent task is finished? For example, you have a main issue with subtasks 1, 2, and 3. If possible, how can I link these subtasks to make them dependent on each other (i.e. subtask 2 can't be started until subtask 1 is finished, etc...)? Also if it's possible for me to do that, can I create a notification that will alert the assignee on subtask 2 when the assignee of subtask 1 marks it done?