Migrating to new gitlab server, losing issue assignees

We have two servers, servera and serverb. Both are configured to use LDAP.

When we migrate projects between these servers, all user information is lost, most obviously issue assignments. This is true both for users who have activated their account on the new server, and those who have not. It is also true for users who have their email address set correctly in their profile.

My expectation is that because we are using LDAP in both cases that there should be no issue authoritatively determining a user mapping.

Is there any way to get robust migration when using LDAP?

As a provisional solution, you can save all user information with an API call on the old server and then provision new users with identical information on the new server.