Hi,
Have you tried to provide edit_user capability to power user? Here is description of edit_user capability.
edit_user Lets the user create, edit, or remove users. A role with the edit_user capability can assign any role to other users. To limit this ability, configure grantableRoles in authorize.conf. For example: grantableRoles = role1;role2;role3. Also lets a user manage certificates for distributed search.
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