Usernames not fully anonymized in issue history

Issue Summary

When anonymizing a user who has an an anonymous userKey (already anonymized or created in Jira version >= 8.4) the full names in the issue history remain unchanged.

Steps to Reproduce

1. Create an user with Jira version >= 8.9,
2. Create a custom field with type "User Picker (multiple users)" and assign it to project screens
3. Create a new issue and fill the User Picker field value with the username from step 1.
4. Anonymize the user

Expected Results

Username in the issue history is changed to the user's anonymous username

Actual Results

Username in the issue history remains unchanged

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available