2nd Cell tries to create another UserNamespace upon login

When following the GDK instructions to create another Cell: https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/howto/cells.md?ref_type=heads

Upon login with the root user on the 2nd cell http://localhost:3001, I get the following error

Because when the current_user is updated, apparently ensure_namespace_correct tries to save the UserNamespace, but because it's not found on the 2nd cell, it tries to create it then it fails because of a conflict on routes.path.

Steps to reproduce the problem:

1. Create the 2nd cell
2. Login immediately with the root user.

How to temporarily suppress the problem

Prevent the UserNamespace from being created on the 2nd cell, but adding a return at the beginning of the ensure_namespace_correct method.

Suggestions to solve this problem. Please feel free to add more

1. UserNamespace should not be persisted when clusterside_main has database_tasks: false
2. The 2nd cell should know that it's the 2nd cell, and never persist Usernamespaces, and maybe some other classes?
3. #421597 (comment 1513044261)

CC: @tkuah @manojmj