MailService.prototype.sendTemplate(template: string,message: Omit<MailMessage, "html" | "text">,data: Readonly<Record<string, unknown>>): Promise<void>
Renders a named template and sends the result. The subject is taken
verbatim from message; the template supplies the html/text bodies.
message: Omit<MailMessage, "html" | "text">
Envelope (recipients, subject, optional from/cc/bcc)