feat: add email notification service with SMTP support

- Create pkg/email package (sender, templates, types)
- SMTP client with TLS, rate limiting, async sending
- HTML email templates with GooSeek branding
- Integrate welcome + password reset emails in auth-svc
- Add limit warning emails (80%/100%) in llm-svc middleware
- Add space invite endpoint with email notification in thread-svc
- Add GetUserEmail helper in JWT middleware
- Add SMTP config to .env, config.go, K8s configmap

Made-with: Cursor

backend/pkg/email/sender.go

@@ -0,0 +1,214 @@
+package email
+
+import (
+	"crypto/tls"
+	"fmt"
+	"log"
+	"net/smtp"
+	"strings"
+	"sync"
+	"time"
+)
+
+type Sender struct {
+	cfg      SMTPConfig
+	mu       sync.Mutex
+	lastSend map[string]time.Time
+}
+
+func NewSender(cfg SMTPConfig) *Sender {
+	return &Sender{
+		cfg:      cfg,
+		lastSend: make(map[string]time.Time),
+	}
+}
+
+func (s *Sender) IsConfigured() bool {
+	return s.cfg.Host != "" && s.cfg.User != "" && s.cfg.Password != ""
+}
+
+func (s *Sender) SendWelcome(to, name string) error {
+	data := WelcomeData{
+		Name:    name,
+		SiteURL: s.cfg.SiteURL,
+	}
+	html := renderTemplate(TypeWelcome, data, s.cfg.SiteName, s.cfg.SiteURL)
+	return s.send(to, fmt.Sprintf("Добро пожаловать в %s!", s.cfg.SiteName), html)
+}
+
+func (s *Sender) SendEmailVerification(to, name, verifyURL string) error {
+	data := EmailVerifyData{
+		Name:      name,
+		VerifyURL: verifyURL,
+	}
+	html := renderTemplate(TypeEmailVerify, data, s.cfg.SiteName, s.cfg.SiteURL)
+	return s.send(to, "Подтвердите ваш email", html)
+}
+
+func (s *Sender) SendPasswordReset(to, name, resetURL string) error {
+	data := PasswordResetData{
+		Name:     name,
+		ResetURL: resetURL,
+	}
+	html := renderTemplate(TypePasswordReset, data, s.cfg.SiteName, s.cfg.SiteURL)
+	return s.send(to, "Сброс пароля", html)
+}
+
+func (s *Sender) SendLimitWarning(to, name string, usageCount, limitCount int, tier string) error {
+	if s.isRateLimited(to, TypeLimitWarning) {
+		return nil
+	}
+
+	percentage := 0
+	if limitCount > 0 {
+		percentage = (usageCount * 100) / limitCount
+	}
+
+	data := LimitWarningData{
+		Name:       name,
+		UsageCount: usageCount,
+		LimitCount: limitCount,
+		Percentage: percentage,
+		Tier:       tier,
+		UpgradeURL: s.cfg.SiteURL + "/pricing",
+	}
+
+	subject := fmt.Sprintf("Вы использовали %d%% лимита запросов", percentage)
+	if percentage >= 100 {
+		subject = "Лимит запросов исчерпан"
+	}
+
+	html := renderTemplate(TypeLimitWarning, data, s.cfg.SiteName, s.cfg.SiteURL)
+	return s.send(to, subject, html)
+}
+
+func (s *Sender) SendSpaceInvite(to, inviterName, spaceName, inviteURL string) error {
+	data := SpaceInviteData{
+		InviterName: inviterName,
+		SpaceName:   spaceName,
+		InviteURL:   inviteURL,
+	}
+	html := renderTemplate(TypeSpaceInvite, data, s.cfg.SiteName, s.cfg.SiteURL)
+	return s.send(to, fmt.Sprintf("%s приглашает вас в Space «%s»", inviterName, spaceName), html)
+}
+
+func (s *Sender) SendSystemAlert(to, title, message, details string) error {
+	data := SystemAlertData{
+		Title:   title,
+		Message: message,
+		Details: details,
+	}
+	html := renderTemplate(TypeSystemAlert, data, s.cfg.SiteName, s.cfg.SiteURL)
+	return s.send(to, fmt.Sprintf("[%s] %s", s.cfg.SiteName, title), html)
+}
+
+func (s *Sender) send(to, subject, htmlBody string) error {
+	if !s.IsConfigured() {
+		log.Printf("[email] SMTP not configured, skipping email to %s: %s", to, subject)
+		return nil
+	}
+
+	headers := map[string]string{
+		"From":                      s.cfg.From,
+		"To":                        to,
+		"Subject":                   subject,
+		"MIME-Version":              "1.0",
+		"Content-Type":              "text/html; charset=UTF-8",
+		"X-Mailer":                  "GooSeek Notification Service",
+		"List-Unsubscribe":          fmt.Sprintf("<%s/settings/notifications>", s.cfg.SiteURL),
+		"List-Unsubscribe-Post":     "List-Unsubscribe=One-Click",
+	}
+
+	var msg strings.Builder
+	for k, v := range headers {
+		msg.WriteString(fmt.Sprintf("%s: %s\r\n", k, v))
+	}
+	msg.WriteString("\r\n")
+	msg.WriteString(htmlBody)
+
+	addr := fmt.Sprintf("%s:%d", s.cfg.Host, s.cfg.Port)
+	auth := smtp.PlainAuth("", s.cfg.User, s.cfg.Password, s.cfg.Host)
+
+	var sendErr error
+	if s.cfg.TLS {
+		sendErr = s.sendTLS(addr, auth, to, msg.String())
+	} else {
+		sendErr = smtp.SendMail(addr, auth, s.cfg.User, []string{to}, []byte(msg.String()))
+	}
+
+	if sendErr != nil {
+		log.Printf("[email] Failed to send to %s: %v", to, sendErr)
+		return fmt.Errorf("failed to send email: %w", sendErr)
+	}
+
+	log.Printf("[email] Sent '%s' to %s", subject, to)
+	return nil
+}
+
+func (s *Sender) sendTLS(addr string, auth smtp.Auth, to, msg string) error {
+	tlsConfig := &tls.Config{
+		ServerName: s.cfg.Host,
+		MinVersion: tls.VersionTLS12,
+	}
+
+	conn, err := tls.Dial("tcp", addr, tlsConfig)
+	if err != nil {
+		return fmt.Errorf("TLS dial failed: %w", err)
+	}
+
+	client, err := smtp.NewClient(conn, s.cfg.Host)
+	if err != nil {
+		conn.Close()
+		return fmt.Errorf("SMTP client creation failed: %w", err)
+	}
+	defer client.Close()
+
+	if err := client.Auth(auth); err != nil {
+		return fmt.Errorf("SMTP auth failed: %w", err)
+	}
+
+	if err := client.Mail(s.cfg.User); err != nil {
+		return fmt.Errorf("SMTP MAIL FROM failed: %w", err)
+	}
+
+	if err := client.Rcpt(to); err != nil {
+		return fmt.Errorf("SMTP RCPT TO failed: %w", err)
+	}
+
+	w, err := client.Data()
+	if err != nil {
+		return fmt.Errorf("SMTP DATA failed: %w", err)
+	}
+
+	if _, err := w.Write([]byte(msg)); err != nil {
+		return fmt.Errorf("SMTP write failed: %w", err)
+	}
+
+	if err := w.Close(); err != nil {
+		return fmt.Errorf("SMTP close failed: %w", err)
+	}
+
+	return client.Quit()
+}
+
+func (s *Sender) isRateLimited(to string, notifType NotificationType) bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	key := fmt.Sprintf("%s:%s", to, notifType)
+	if last, ok := s.lastSend[key]; ok {
+		if time.Since(last) < 24*time.Hour {
+			return true
+		}
+	}
+	s.lastSend[key] = time.Now()
+	return false
+}
+
+func (s *Sender) SendAsync(fn func() error) {
+	go func() {
+		if err := fn(); err != nil {
+			log.Printf("[email] Async send error: %v", err)
+		}
+	}()
+}