admin should be allowed to elevate user from role `User` to `Domain Admin`

[DaanHoogland]

ISSUE TYPE

• Bug Report

COMPONENT NAME

UI / API

CLOUDSTACK VERSION

CONFIGURATION

OS / ENVIRONMENT

SUMMARY

as noticed in #9012 (comment)

When an admin want to grant domain admin rights to a user with role user:

This is true in ROOT, where it maybe should fail but with a better message. In a subdomain this would be a perfectly acceptable action.

STEPS TO REPRODUCE

EXPECTED RESULTS

ACTUAL RESULTS