[Nova][Keystone] Instance boot fail if user has many roles

Hi Nova and Keystone folks,

I'd like to your feedback for the bug[1] and the commit[2]. We use Keystone as company internal role management system and hit the issue frequently.

The commit is to change instance_system_metadata table schema, but it could be too big change only for the long role list.

Another idea I can imagine is to introduce "store_boot_roles" boolean configuration to store the boot_roles or not. IIUC, the boot_roles is used only for a specific vendor data in the metadata api.

If there is another good value to store from Keystone side, I'm happy to use the value instead of role name, too.

1. https://bugs.launchpad.net/nova/+bug/2075100 2. https://review.opendev.org/c/openstack/nova/+/925163

thank you, Masahito