Export an object with an attribute of type User with the User friendly format. The exported value of the user will be represented with the full name. If we use Data consistent format instead, some users will be represented with their userkey that looks like JIRAUSER12345 and some users with their username.

This is due to the export uses userkey of Users. And officially since 8.4, newly created users have their userkey different from username, which is in the format of JIRAUSER<number>. Existing users still have their userkey=username and hence, after Jira upgrade, we'll see a different types of userkeys.

Use username instead of userkey for object export, or allow this to be configured somewhere