Email subjects

An email's subject line is translated like a message. The email's member in its domain's language files is the subject, with the email's fields as placeholders. Its body is its .html and .txt templates (Email).

A subject is worded where its emails are written, checked when a language file words it, and isn't a call. It is required in every supported locale that isn't in progress, as a message's wording is.

translations {    welcome_email: "Welcome, {display_name}"}