Create unique name using user template

Would like to use user template to populate a unique name attribute; i.e. provide givenName + lastname as input to create a unique name & fullName attributes. I have fullName generated by the current template; tried copying logic and add iterator.

I see a similar request for 3.0 (e.g. MID-1771), but no indication of how to use feature. I assume it was ported to 3.1.1. Attached my attempted template.