Right now the org admin works "by accident". That works in UI and for API the similar can be achieved by #16363. But in ideal case, available organizations should work based on view_organizations and assign_organizations permissions. While the feature today is limited to a single organization, we should support delegation for multiple organizations.

Reproducing steps (in both UI and API)
0. create a user with org admin role assigned to 2 organizations
1. try creating a new domain
2. it will always fail without any error message in UI, the issue is in fact that the taxonomy assignment is disallowed until user gets view_organizations and assign_organizations permissions

• After gets Org admin role (which is assigned to one or more orgs) and he's assigned to these organizations, they can create/edit resources in these.
• This means organization filters need to be assignable to organizations (requires scoped_search definition)