Fixing project namespace traversal_ids syncing

What does this MR do and why?

Addressing this issue from customer: #387844 (closed)

This will fix the syncing of the traversal_ids of the ProjectNamespaces when the feature flag use_traversal_ids_for_ancestors is disabled.

The original problem has been explained in details here: #388820 (closed)

How to set up and validate locally

You can test this using the rails console on both master and this branch, and see the difference.

Steps to validate locally

Create the test data

To make the setup look like self-managed

Feature.disable(:use_traversal_ids_for_ancestors)

Create group1, group2 and project_namespace

g1 = FactoryBot.create(:group, name: "test" + (0...6).map { (65 + rand(26)).chr }.join); nil
g2 = FactoryBot.create(:group, name: "test" + (0...6).map { (65 + rand(26)).chr }.join,parent: g1); nil
p = FactoryBot.create(:project_namespace, name: "test" + (0...8).map { (65 + rand(26)).chr }.join, parent: g2); nil

If creating the project_namespace fails due to a conflict on the path/name, create it again.

reload the traversal_ids on the two groups

[g1, g2, p].each(&:reload); nil

Sync the namespaces to the CI side

Namespaces::SyncEvent.all.each { |e| Ci::NamespaceMirror.sync!(e) }; nil
Namespaces::SyncEvent.delete_all

Print the traversal_ids of the source namespaces

[g1, g2, p].each { |n| puts n.traversal_ids.inspect }; nil

Print the traversal_ids of the CI mirrored objects

This will print the wrong traversal_ids on master, but the correct traversal_ids on this branch

[g1, g2, p].each { |n| puts n.ci_namespace_mirror.traversal_ids.inspect }; nil

Clean Up

[g1, g2, p].each(&:delete)
Namespaces::SyncEvent.delete_all

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #387844 (closed)