refactor: backend tenant_group 제거 및 관련 정리

backend/internal/domain/tenant_group.go

@@ -1,32 +0,0 @@
-package domain
-
-import (
-	"time"
-
-	"github.com/google/uuid"
-	"gorm.io/gorm"
-)
-
-// TenantGroup represents a collection of tenants.
-type TenantGroup struct {
-	ID          string         `gorm:"primaryKey;type:uuid;default:gen_random_uuid()" json:"id"`
-	Name        string         `gorm:"not null" json:"name"`
-	Slug        string         `gorm:"uniqueIndex;not null" json:"slug"`
-	Description string         `json:"description"`
-	Tenants     []Tenant       `gorm:"foreignKey:TenantGroupID" json:"tenants,omitempty"`
-	Config      JSONMap        `gorm:"type:jsonb" json:"config,omitempty"`
-	CreatedAt   time.Time      `json:"createdAt"`
-	UpdatedAt   time.Time      `json:"updatedAt"`
-	DeletedAt   gorm.DeletedAt `gorm:"index" json:"-"`
-}
-
-func (tg *TenantGroup) TableName() string {
-	return "tenant_groups"
-}
-
-func (tg *TenantGroup) BeforeCreate(tx *gorm.DB) (err error) {
-	if tg.ID == "" {
-		tg.ID = uuid.NewString()
-	}
-	return
-}