Option for unified customer name field

Separating names into "first name" and "last name", and then referring to people by their first name, is a pretty anglo-centric approach.  Other cultures have other conventions.  For my case, in China it's *way* too familiar for a business to refer to a customer by their given name.

The best culturally-neutral approach is just to have a simple free text field for the name and let people tell you how they want you to refer to them.  This is especially true when the name is only needed "to personalize your account experience."

This change provides an option to switch between first name / last name and simple name field.