Portal-only user accounts cannot allow access to view their email addresses

Issue Summary

With the recent GDPR changes to allow restrictions for profile information:
https://confluence.atlassian.com/cloud/update-your-profile-and-visibility-settings-968656104.html

These changes impact the visibility of Portal-only users, however, those users have no means by which to allow visibility to the email addresses.
This can cause a great deal of confusion as Service Desk agents cannot know which email address they are replying to or adding as request participants by peeking the user details by hovering over the user.

Steps to Reproduce

1. Create a Jira Service Desk portal-only user
2. Have that user create an issue
3. Open the issue as a non-site-admin service desk agent
4. Attempt to determine the email address of the user

Expected Results

Hovering over the user shows the user card with the email address.

Actual Results

The card does not show on hover and in places where it does show does not show the email address of the user.

Notes

The email address does get listed in the "customers" page of the project, however, if the friendly names of two users are identical, it is impossible to tell the two apart in the context of an issue.

Workaround

Currently the closest workaround is to request that your customers set their friendly name to either be their email address, or to be something highly unique.