Do not allow to mention a people which is not invited to the project via @name

Problem We have some code which uses @ symbol, which is defined in the quire as a "mention" tag. Means @someone.

We found out that we mention many people because of that, which is very insecure, bad, and weird.

Suggestion: Add an option to organization / or settings which are block mentioning different people, and not convert the @something to a human which does not belong to the project.

Again, the main purpose of the suggestion is dropping @ tag for calling people which is not a part of the project/organization.

How feature must look in result

1. I enter @something bla bla bla
2. This, for example, @something it's a real user in quire. By default, that means we are mentioning him, and he will receive notifications (as far as I understand) and maybe access to the task to read it.
3. This @something user will not be mentioned if we have an option in our settings, and will not be converted as a link to the user which exists in the quire.
4. The @something will not receive any notifications and so on.
5. Overall performance in your own app because of restricting such access to all users in quire will be heavily increased. Because not need every time to parse tons of users via @tag