How to control the execution of tasks in Redmine (observers)?

Question

Access rights

Can you please explain how to implement task execution control in Redmine projects?
In Redmine, I have a group of users who ONLY monitor the execution of tasks in projects (as a rule, heads of various departments of the enterprise), well, they can leave some comments on the task. They are added to the "Observer" group. So it is necessary that when the customer creates a task when choosing observers, the observers receive a notification on the soap and they can see exactly those tasks in which they were assigned as observers by reference. And each member of this group should not see other people's tasks (not his department), where he is not appointed as an observer.
The fact is that if in the rights of the "Observer" group you assign the visibility "Tasks created or assigned to a user", then a member of this group, when appointed in a task as an observer, does not receive a notification by mail and, accordingly, does not see this task. And he does not see any tasks at all.
If, however, in the rights of the "Observer" group, the visibility is set to "All tasks" or "Only general tasks", then a member of this group, when appointed as an observer in a task, receives a notification by mail and sees this task. BUT he also sees other tasks where he is not assigned as an observer, which, accordingly, does not suit my needs in any way.
I can't understand what is the point of Redmine's Observers? And how can I implement what I need?
Help me please.

Answer 1

The meaning of redmine observers is to receive notifications by email in tasks that you already see, but are not assigned to you. That is, observers do not expand the rights of users in any way and are not associated with them.