Ability to set domain restriction for private Service Desk to allow self-sign up.

Issue Summary

Currently, in the "Customer Permission" level, you can either set for public sign-up or privatized Service Desk which requires the Service Desk Agent to send invites in order for the customer to access the project.

There is no in-between option and the customer permission works in either absolutes.

Suggested Solution

It would be great if there is an option to allow the creation of a private Service Desk which comes with the ability to set domain white-listing for a specific group of customers.

This allows the customer to send issues directly to the private Service Desk without the need of the Service Desk Agents to send invites.

Any other customers who are not within the domain allowance won't be able to send emails to the private Service Desk.