CSV export should contain display names for user picker field like reporter and assignee fields

Issue Summary
Currently, the CSV file exported from the search result contains username for user picker fields such as Reporter and Assignee fields when the user has been invited from the Project itself. This causes the users to appear as not human-readable values/strings in assignee and reporter fields.

Steps to Reproduce
1. Go to the Project's People section.
2. Click "Add People" > Add a new user to your instance.
3. This adds the new user as Atlassian Account ID in the Username table.

Expected Results
The best result would be that the CSV file contains a display name or email address for the reporter and assignee field.

Actual Results
The username appears in the assignee field which will be a AAID.