Add direct serving of package content (#25543)

Fixes #24723

Direct serving of content aka HTTP redirect is not mentioned in any of
the package registry specs but lots of official registries do that so it
should be supported by the usual clients.

routers/api/packages/pypi/pypi.go

@@ -80,7 +80,7 @@ func DownloadPackageFile(ctx *context.Context) {
 	packageVersion := ctx.Params("version")
 	filename := ctx.Params("filename")
 
-	s, pf, err := packages_service.GetFileStreamByPackageNameAndVersion(
+	s, u, pf, err := packages_service.GetFileStreamByPackageNameAndVersion(
 		ctx,
 		&packages_service.PackageInfo{
 			Owner:       ctx.Package.Owner,
@@ -100,12 +100,8 @@ func DownloadPackageFile(ctx *context.Context) {
 		apiError(ctx, http.StatusInternalServerError, err)
 		return
 	}
-	defer s.Close()
 
-	ctx.ServeContent(s, &context.ServeHeaderOptions{
-		Filename:     pf.Name,
-		LastModified: pf.CreatedUnix.AsLocalTime(),
-	})
+	helper.ServePackageFile(ctx, s, u, pf)
 }
 
 // UploadPackageFile adds a file to the package. If the package does not exist, it gets created.