feat: Implement notification service and integrate with user interactions

- Added notification service to handle sending and listing notifications.
- Integrated notification sending on user follow and order payment events.
- Updated user service to include fetching followed tenants.
- Enhanced content service to manage access control for content assets.
- Implemented logic for listing content topics based on genre.
- Updated creator service to manage content updates and pricing.
- Improved order service to include detailed order information and notifications.
- Added tests for notification CRUD operations and order details.

backend/app/services/tenant.go

@@ -61,7 +61,8 @@ func (s *tenant) Follow(ctx context.Context, id string) error {
 	tid := cast.ToInt64(id)
 
 	// Check if tenant exists
-	if _, err := models.TenantQuery.WithContext(ctx).Where(models.TenantQuery.ID.Eq(tid)).First(); err != nil {
+	t, err := models.TenantQuery.WithContext(ctx).Where(models.TenantQuery.ID.Eq(tid)).First()
+	if err != nil {
 		return errorx.ErrRecordNotFound
 	}
 
@@ -75,6 +76,10 @@ func (s *tenant) Follow(ctx context.Context, id string) error {
 	if err := models.TenantUserQuery.WithContext(ctx).Save(tu); err != nil {
 		return errorx.ErrDatabaseError.WithCause(err)
 	}
+
+	if Notification != nil {
+		_ = Notification.Send(ctx, t.UserID, "interaction", "新增粉丝", "有人关注了您的店铺: "+t.Name)
+	}
 	return nil
 }