Allow agent to invite Customer when public signup is off

Problem Definition

When public signup is set to off (Request security is set to "Only people who have an account can raise a request") JIRA Service Desk agent won't be able to invite new customers (the Invite customers button is missing in the Customers page). However project Administrators are still able to invite new customers.

Suggested Solution

When public signup is turned off in for a Service Desk project:

• Allow Service Desk agent to invite new customers via Customers page
• Allow both Service Desk agent and administrators to invite new customers during creation of new ticket on behalf of that new customer (see screenshot below, this is currently possible only when public signup is turned on)