Raw SMTP adapter using Swoosh's SMTP adapter directly. Does not require a host-app Mailer module — reads SMTP config from AuditTrail config.

Config:

config :audit_trail,
  mailer_adapter: {AuditTrail.Adapters.SMTP, []},
  from_email:     {"MyApp Alerts", "alerts@myapp.com"},
  smtp: [
    relay:    "smtp.gmail.com",
    username: "alerts@myapp.com",
    password: System.get_env("SMTP_PASSWORD"),
    port:     587,
    tls:      :always,
    auth:     :always
  ]