feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

internal/notify/email.go

@@ -0,0 +1,57 @@
+// Package notify delivers notifications using credentials persisted in the
+// notification_credentials table. It is the credential-backed counterpart to
+// the legacy secrets.yml driven senders in internal/sender and internal/tg.
+package notify
+
+import (
+	"crypto/tls"
+	"fmt"
+
+	"gopkg.in/gomail.v2"
+
+	"rsgit.ru/rsmon/rsmon/app/models"
+)
+
+// Email sends an email using the given SMTP credential. bodyText is sent as
+// text/plain and, when non-empty, bodyHTML is added as a text/html alternative
+// so the recipient's MUA picks the best representation.
+func Email(cred *models.NotificationCredential, to, subject, bodyText, bodyHTML string) error {
+	if cred == nil {
+		return fmt.Errorf("credential is nil")
+	}
+	if cred.Kind != models.CredentialKindSMTP {
+		return fmt.Errorf("credential %d is not smtp (kind=%s)", cred.ID, cred.Kind)
+	}
+	if cred.Server == nil || cred.Port == nil || cred.Login == nil || cred.FromAddr == nil {
+		return fmt.Errorf("credential %d missing required smtp fields", cred.ID)
+	}
+
+	password, err := cred.GetSecret()
+	if err != nil {
+		return fmt.Errorf("decrypt smtp password: %w", err)
+	}
+
+	fromName := "RSMon"
+	if cred.FromName != nil && *cred.FromName != "" {
+		fromName = *cred.FromName
+	}
+
+	m := gomail.NewMessage()
+	m.SetHeader("From", m.FormatAddress(*cred.FromAddr, fromName))
+	m.SetHeader("To", to)
+	m.SetHeader("Subject", subject)
+	m.AddAlternative("text/plain", bodyText)
+	if bodyHTML != "" {
+		m.AddAlternative("text/html", bodyHTML)
+	}
+
+	d := gomail.NewDialer(*cred.Server, *cred.Port, *cred.Login, password)
+	if cred.InsecureSkipVerify {
+		d.TLSConfig = &tls.Config{InsecureSkipVerify: true}
+	}
+
+	if err := d.DialAndSend(m); err != nil {
+		return fmt.Errorf("send smtp via credential %d: %w", cred.ID, err)
+	}
+	return nil
+}