feat: Introduce MediaAssetVariant for better asset management

- Added MediaAssetVariant enum with values 'main' and 'preview'.
- Updated media asset service logic to utilize MediaAssetVariant for variant handling.
- Refactored database models and queries to include variant and source_asset_id fields.
- Enhanced validation for asset variants in upload and processing functions.
- Updated Swagger documentation to reflect new variant structure and descriptions.
- Implemented necessary database migrations to support the new variant constraints.

backend/app/services/media_delivery.go

@@ -12,7 +12,6 @@ import (
 
 	jwtlib "github.com/golang-jwt/jwt/v4"
 	log "github.com/sirupsen/logrus"
-	"go.ipao.vip/gen/types"
 	"gorm.io/gorm"
 )
 
@@ -126,10 +125,13 @@ func (s *mediaDelivery) ResolvePlayRedirect(ctx context.Context, tenantID int64,
 		"exp":            claims.ExpiresAt,
 	}).Info("services.media_delivery.resolve_play_redirect")
 
-	var asset models.MediaAsset
-	if err := _db.WithContext(ctx).
-		Where("tenant_id = ? AND id = ? AND deleted_at IS NULL", tenantID, claims.AssetID).
-		First(&asset).Error; err != nil {
+	tblAsset, queryAsset := models.MediaAssetQuery.QueryContext(ctx)
+	asset, err := queryAsset.Where(
+		tblAsset.TenantID.Eq(tenantID),
+		tblAsset.ID.Eq(claims.AssetID),
+		tblAsset.DeletedAt.IsNull(),
+	).First()
+	if err != nil {
 		if errors.Is(err, gorm.ErrRecordNotFound) {
 			return "", errorx.ErrRecordNotFound.WithMsg("media asset not found")
 		}
@@ -140,16 +142,13 @@ func (s *mediaDelivery) ResolvePlayRedirect(ctx context.Context, tenantID int64,
 	}
 
 	// 二次校验：token 必须对应“该内容 + 该角色”的绑定关系，避免 token 被滥用到非预期内容。
-	var ca models.ContentAsset
-	if err := _db.WithContext(ctx).
-		Where(
-			"tenant_id = ? AND content_id = ? AND asset_id = ? AND role = ?",
-			tenantID,
-			claims.ContentID,
-			claims.AssetID,
-			claims.Role,
-		).
-		First(&ca).Error; err != nil {
+	tblCA, queryCA := models.ContentAssetQuery.QueryContext(ctx)
+	if _, err := queryCA.Where(
+		tblCA.TenantID.Eq(tenantID),
+		tblCA.ContentID.Eq(claims.ContentID),
+		tblCA.AssetID.Eq(claims.AssetID),
+		tblCA.Role.Eq(claims.Role),
+	).First(); err != nil {
 		if errors.Is(err, gorm.ErrRecordNotFound) {
 			return "", errorx.ErrRecordNotFound.WithMsg("content asset binding not found")
 		}
@@ -162,7 +161,6 @@ func (s *mediaDelivery) ResolvePlayRedirect(ctx context.Context, tenantID int64,
 	case "stub":
 		return "", errorx.ErrServiceUnavailable.WithMsg("storage provider not configured")
 	default:
-		_ = types.JSON(asset.Meta) // keep meta referenced for future extensions
 		return "", errorx.ErrServiceUnavailable.WithMsg("storage provider not implemented: " + asset.Provider)
 	}
 }