feat(backend): implement dynamic multi-tenancy routing and CORS

backend/internal/handler/auth_handler.go

@@ -538,6 +538,55 @@ func (h *AuthHandler) getBearerToken(c *fiber.Ctx) string {
 	return parts[1]
 }
 
+func (h *AuthHandler) resolveUserfrontURL(c *fiber.Ctx) string {
+	// 1. Try to use the Host header from the request
+	host := c.Get("X-Forwarded-Host")
+	if host == "" {
+		host = c.Hostname()
+	}
+
+	// 2. Determine scheme
+	scheme := "https"
+	if os.Getenv("APP_ENV") == "dev" || os.Getenv("APP_ENV") == "" || c.Protocol() == "http" {
+		scheme = "http"
+	}
+
+	// 3. Fallback to env if host is not available or is localhost (and not in dev)
+	envURL := os.Getenv("USERFRONT_URL")
+	if envURL == "" {
+		envURL = "http://sso.hmac.kr"
+	}
+
+	if host == "" || (host == "localhost" && os.Getenv("APP_ENV") != "dev") {
+		return strings.TrimRight(envURL, "/")
+	}
+
+	return fmt.Sprintf("%s://%s", scheme, host)
+}
+
+func (h *AuthHandler) GetTenantInfo(c *fiber.Ctx) error {
+	tenantID, _ := c.Locals("tenant_id").(string)
+	if tenantID == "" {
+		return c.JSON(fiber.Map{
+			"isCentral": true,
+		})
+	}
+
+	tenant, err := h.TenantService.GetTenant(c.Context(), tenantID)
+	if err != nil {
+		return errorJSON(c, fiber.StatusNotFound, "Tenant not found")
+	}
+
+	return c.JSON(fiber.Map{
+		"isCentral":   false,
+		"id":          tenant.ID,
+		"name":        tenant.Name,
+		"slug":        tenant.Slug,
+		"description": tenant.Description,
+		"type":        tenant.Type,
+	})
+}
+
 // normalizePhoneForLoginID는 전화번호를 IDP 조회에 적합한 형태(E.164)로 정규화합니다.
 func normalizePhoneForLoginID(phone string) string {
 	normalized := strings.ReplaceAll(phone, "-", "")
@@ -920,10 +969,7 @@ func (h *AuthHandler) InitEnchantedLink(c *fiber.Ctx) error {
 		return errorJSON(c, fiber.StatusNotFound, "User not registered")
 	}
 
-	userfrontURL := os.Getenv("USERFRONT_URL")
-	if userfrontURL == "" {
-		userfrontURL = "http://sso.hmac.kr"
-	}
+	userfrontURL := h.resolveUserfrontURL(c)
 	if req.URI != "" {
 		userfrontURL = req.URI
 	}
@@ -1692,14 +1738,7 @@ func (h *AuthHandler) InitiatePasswordReset(c *fiber.Ctx) error {
 		return errorJSON(c, fiber.StatusInternalServerError, "Authentication service not configured")
 	}
 
-	userfrontURL := os.Getenv("USERFRONT_URL")
-	if userfrontURL == "" {
-		ale.Status = fiber.StatusInternalServerError
-		ale.LatencyMs = time.Since(startTime)
-		ale.ProviderError = "USERFRONT_URL is not set"
-		ale.Log(slog.LevelError, "USERFRONT_URL is not set")
-		return errorJSON(c, fiber.StatusInternalServerError, "USERFRONT_URL environment variable is not set")
-	}
+	userfrontURL := h.resolveUserfrontURL(c)
 	// [Changed] Point to Backend API for verification (which then redirects to Frontend)
 	redirectURL := fmt.Sprintf("%s/api/v1/auth/password/reset/verify", userfrontURL)
 	ale.RedirectTo = redirectURL
@@ -1863,10 +1902,7 @@ func (h *AuthHandler) ProcessPasswordResetToken(c *fiber.Ctx) error {
 	ale.LoginIDs["loginId"] = loginID
 	ale.LoginIDs["loginId_normalized"] = loginID
 
-	userfrontURL := strings.TrimRight(os.Getenv("USERFRONT_URL"), "/")
-	if userfrontURL == "" {
-		userfrontURL = "https://sso.hmac.kr"
-	}
+	userfrontURL := h.resolveUserfrontURL(c)
 	redirectBase, parseErr := url.Parse(userfrontURL + "/reset-password")
 	if parseErr != nil {
 		ale.Status = fiber.StatusInternalServerError
@@ -2000,10 +2036,7 @@ func (h *AuthHandler) InitQRLogin(c *fiber.Ctx) error {
 	}
 
 	// QR 코드 페이로드를 실제 접속 가능한 URL로 변경합니다.
-	userfrontURL := os.Getenv("USERFRONT_URL")
-	if userfrontURL == "" {
-		userfrontURL = "https://sso.hmac.kr"
-	}
+	userfrontURL := h.resolveUserfrontURL(c)
 	qrPayload := fmt.Sprintf("%s/ql/%s", strings.TrimRight(userfrontURL, "/"), qrRef)
 
 	slog.Info("[QR] Init", "pendingRef", pendingRef, "qrRef", qrRef, "url", qrPayload)