refactor(tvix/nar-bridge): move blob cb function to pkg/importer

This is useful outside a HTTP server scenario.

Change-Id: If35f1ab245855378fd01f16ad7b5774d0cf590ba
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9532
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>

tvix/nar-bridge/pkg/server/nar_put.go

@@ -43,7 +43,7 @@ func registerNarPut(s *Server) {
 			ctx,
 			// buffer the body by 10MiB
 			bufio.NewReaderSize(r.Body, 10*1024*1024),
-			genBlobServiceWriteCb(ctx, s.blobServiceClient),
+			importer.GenBlobUploaderCb(ctx, s.blobServiceClient),
 			func(directory *castorev1pb.Directory) ([]byte, error) {
 				return directoriesUploader.Put(directory)
 			},