Add user emails to space exports instead of Atlassian Account ID (AAID)

Current SItuation

Space exports currently export users with their AAID instead of emails. If a customer wants to export users with their emails he/she would have to do a full site backup.

Desired Situation

This is not ideal when doing space exports, instead, admins should be able to choose between exporting spaces with users' emails or AAID.

This could be useful for syncing up an already existing userbase with imported Spaces.