Don't use trans clients' deadname in email subjects or recipient names

I'm trans and most of my clients are trans, and many have huge sensitivity around seeing their deadname. Legal names must be used on legal documents but legal name is NOT required for communications. Instead a Preferred name is present for a client Bright could pull that text string to use in auto-email subject lines and addressee names - using the same logic as is now used for the %FIRSTNAME% field in templates.