feat: 커스텀 필드 기반 로그인 ID 연동 기능 추가 (#440)

- Kratos Identity 스키마에 로그인 전용 `id` 속성 추가
- 테넌트 Config의 `loginIdField` 설정에 따라 User의 `login_id` 및 Kratos `traits.id` 동기화 로직 구현
- Admin UI 테넌트 스키마 설정 내 '로그인 ID로 사용' 체크박스 추가
- Admin UI 사용자 생성/수정/조회 화면에 로그인 ID 관리 필드 및 컬럼 반영
- Userfront 로그인 화면 접속 시 테넌트 설정에 따라 동적 로그인 ID 라벨 적용
- 관련 다국어(ko/en) 번역 추가 및 로그인 ID 설계 문서 업데이트

backend/internal/handler/user_handler.go

@@ -321,11 +321,20 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 		"grade":           role,
 	}
 
-	// [Resolve TenantID before Kratos creation]
+	// [Resolve TenantID and LoginID before Kratos creation]
 	var tenantID string
 	if req.CompanyCode != "" && h.TenantService != nil {
 		if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), req.CompanyCode); err == nil && tenant != nil {
 			tenantID = tenant.ID
+
+			// Sync custom field to LoginID if configured
+			if loginIDField, ok := tenant.Config["loginIdField"].(string); ok && loginIDField != "" {
+				if val, exists := req.Metadata[loginIDField]; exists {
+					if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
+						attributes["id"] = loginIDStr
+					}
+				}
+			}
 		}
 	}
 	attributes["role"] = role
@@ -333,6 +342,11 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 		attributes["tenant_id"] = tenantID
 	}
 
+	// [Override with explicit LoginID if provided]
+	if req.LoginID != "" {
+		attributes["id"] = req.LoginID
+	}
+
 	// Merge custom metadata into attributes
 	for k, v := range req.Metadata {
 		// Don't overwrite core fields
@@ -343,6 +357,7 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 
 	brokerUser := &domain.BrokerUser{
 		Email:       email,
+		LoginID:     extractString(attributes, "id"),
 		Name:        name,
 		PhoneNumber: normalizePhoneNumber(req.Phone),
 		Attributes:  attributes,
@@ -413,6 +428,7 @@ func (h *UserHandler) CreateUser(c *fiber.Ctx) error {
 
 type bulkUserItem struct {
 	Email      string         `json:"email"`
+	LoginID    string         `json:"loginId"`
 	Name       string         `json:"name"`
 	Phone      string         `json:"phone"`
 	Role       string         `json:"role"`
@@ -456,9 +472,10 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 
 	// Pre-fetch tenant data to avoid redundant DB calls
 	type tenantCacheItem struct {
-		ID     string
-		Schema []interface{}
-		Groups []domain.UserGroup
+		ID           string
+		Schema       []interface{}
+		Groups       []domain.UserGroup
+		LoginIDField string
 	}
 	tenantCache := make(map[string]tenantCacheItem)
 
@@ -500,6 +517,9 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 				if s, ok := tenant.Config["userSchema"].([]interface{}); ok {
 					tItem.Schema = s
 				}
+				if lf, ok := tenant.Config["loginIdField"].(string); ok {
+					tItem.LoginIDField = lf
+				}
 				// [Fix] Cache user groups for this tenant to match department
 				if h.UserGroupRepo != nil {
 					if groups, err := h.UserGroupRepo.ListByTenantID(c.Context(), tenant.ID); err == nil {
@@ -537,6 +557,20 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 			"role":            role,
 		}
 
+		// Sync LoginID from configured custom field
+		if tItem.LoginIDField != "" {
+			if val, exists := item.Metadata[tItem.LoginIDField]; exists {
+				if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
+					attributes["id"] = loginIDStr
+				}
+			}
+		}
+
+		// Override with explicit LoginID if provided
+		if item.LoginID != "" {
+			attributes["id"] = item.LoginID
+		}
+
 		// Merge metadata
 		for k, v := range item.Metadata {
 			if _, exists := attributes[k]; !exists {
@@ -546,6 +580,7 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 
 		identityID, err := h.OryProvider.CreateUser(&domain.BrokerUser{
 			Email:       email,
+			LoginID:     extractTraitString(attributes, "id"),
 			Name:        item.Name,
 			PhoneNumber: normalizePhoneNumber(item.Phone),
 			Attributes:  attributes,
@@ -571,6 +606,7 @@ func (h *UserHandler) BulkCreateUsers(c *fiber.Ctx) error {
 			localUser := &domain.User{
 				ID:              identityID,
 				Email:           email,
+				LoginID:         extractTraitString(attributes, "id"),
 				Name:            name,
 				Phone:           normalizePhoneNumber(item.Phone),
 				Role:            role,
@@ -1014,6 +1050,7 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 	}
 
 	var req struct {
+		LoginID     *string        `json:"loginId"`
 		Password    *string        `json:"password"`
 		Name        *string        `json:"name"`
 		Phone       *string        `json:"phone"`
@@ -1113,11 +1150,43 @@ func (h *UserHandler) UpdateUser(c *fiber.Ctx) error {
 		traits["role"] = role
 	}
 
+	// [LoginID Sync based on Tenant Settings]
+	schemaCompCode := extractTraitString(traits, "companyCode")
+	if req.CompanyCode != nil {
+		schemaCompCode = *req.CompanyCode
+	}
+	if schemaCompCode != "" && h.TenantService != nil {
+		if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), schemaCompCode); err == nil && tenant != nil {
+			if loginIDField, ok := tenant.Config["loginIdField"].(string); ok && loginIDField != "" {
+				// Search in Metadata (could be flat or namespaced)
+				if val, exists := req.Metadata[loginIDField]; exists {
+					if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
+						traits["id"] = loginIDStr
+					}
+				} else if namespaced, exists := req.Metadata[tenant.ID]; exists {
+					if subMeta, ok := namespaced.(map[string]any); ok {
+						if val, exists := subMeta[loginIDField]; exists {
+							if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
+								traits["id"] = loginIDStr
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// [Override with explicit LoginID if provided]
+	if req.LoginID != nil && *req.LoginID != "" {
+		traits["id"] = *req.LoginID
+	}
+
 	// [Namespaced Metadata Sync]
 	coreTraits := map[string]bool{
 		"email": true, "name": true, "phone_number": true,
 		"grade": true, "companyCode": true, "department": true,
 		"affiliationType": true, "role": true, "tenant_id": true,
+		"id": true,
 	}
 
 	// For namespaced metadata, we don't delete everything, we merge.
@@ -1284,6 +1353,7 @@ func (h *UserHandler) mapToLocalUser(identity service.KratosIdentity) *domain.Us
 	user := &domain.User{
 		ID:              identity.ID,
 		Email:           extractTraitString(traits, "email"),
+		LoginID:         extractTraitString(traits, "id"),
 		Name:            extractTraitString(traits, "name"),
 		Phone:           extractTraitString(traits, "phone_number"),
 		Role:            role,