To have editable UI option to change the Administrator's username of tenant owner via. management tenancy

Issue: Currently the Adminstrator's username field of tenant owner is non-editable on management UI, which causes problems when there is a need to change the tenant owner.

Workaround: Request Software AG team to change it via. backend everytime.

Suggestion: Make the 'Adminstrator's username' field of the tenant owner editable on the management tenancy to mitigate the issue.