Use Sendico SMTP mailbox for local notifications (#57)

backend/notifications/email/driver.go

@@ -19,6 +19,7 @@ type Driver string
 const (
 	SendGrid Driver = "sendgrid"
 	Resend   Driver = "resend"
+	SMTP     Driver = "smtp"
 )
 
 type Config = sharedmodel.DriverConfig[Driver]
@@ -35,6 +36,7 @@ type Outcome struct {
 	RetryAfter time.Duration
 	// Provider diagnostics are sanitized operational data, not public failures.
 	HTTPStatus      int
+	SMTPStatus      int
 	ProviderError   string
 	ProviderMessage string
 }
@@ -50,6 +52,9 @@ type client struct {
 }
 
 func New(config Config) (Sender, error) {
+	if config.Driver == SMTP {
+		return newSMTP(config)
+	}
 	var s Settings
 	decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{Result: &s, ErrorUnused: true, TagName: "mapstructure"})
 	if err != nil {