Horizon Identity Domain Panel is broken in Caracal+

[Pavlo Shchelokovskyy]

Starting with Caracal release, Identity Domains Panel is broken, as it only ever lists that domain that the user belongs to.

Devstack/Master, logged as admin (devstack-admin creds in /etc/openstack/clouds.yaml).

With default Horizon settings, I only ever see Default domain, even if I manually create some more. And I do not have an option to create domains from UI as well. This is because AFAIU the ability to create domains is tied to OPENSTACK_KEYSTONE_MULTIDOMAIN_SUPPORT (False by default), which is waaay legacy IMO. This option is quite overloaded in Horizon code, but that's a different question.

When I enable the OPENSTACK_KEYSTONE_MULTIDOMAIN_SUPPORT in my local_settings.py, I can create domains from UI, but I still can not see any other domain other than the domain of the user.

I tracked it to this piece of code that replaces the scope to the domain one for admins
https://opendev.org/openstack/horizon/src/branch/stable/2024.1/openstack_dashboard/api/keystone.py#L153-L163 ,
plus a recent change in Keystone https://review.opendev.org/c/openstack/keystone/+/900028 that started forcing domain tokens to only be able to list their own domains.