Limit original size of the contents of a site manifest.

The limit is applied to the original size and not compressed size for
predictability and fairness.

src/manifest.go

···
 	return nil
 }
 
+var ErrSiteTooLarge = errors.New("site too large")
 var ErrManifestTooLarge = errors.New("manifest too large")
 
 // Uploads inline file data over certain size to the storage backend. Returns a copy of
···
 		}
 	}
 
-	// Compute the deduplicated storage size.
-	var blobSizes = make(map[string]int64)
+	// Compute the total and deduplicated storage size.
+	totalSize := int64(0)
+	blobSizes := map[string]int64{}
 	for _, entry := range manifest.Contents {
+		totalSize += entry.GetOriginalSize()
 		if entry.GetType() == Type_ExternalFile {
 			blobSizes[string(entry.Data)] = entry.GetCompressedSize()
 		}
+	}
+	if uint64(totalSize) > config.Limits.MaxSiteSize.Bytes() {
+		return nil, fmt.Errorf("%w: contents size %s exceeds %s limit",
+			ErrSiteTooLarge,
+			datasize.ByteSize(totalSize).HR(),
+			config.Limits.MaxSiteSize.HR(),
+		)
 	}
 	for _, blobSize := range blobSizes {
 		*extManifest.StoredSize += blobSize

src/pages.go

···
 
 	switch result.outcome {
 	case UpdateError:
-		if errors.Is(result.err, ErrManifestTooLarge) {
-			w.WriteHeader(http.StatusRequestEntityTooLarge)
+		if errors.Is(result.err, ErrSiteTooLarge) {
+			w.WriteHeader(http.StatusUnprocessableEntity)
+		} else if errors.Is(result.err, ErrManifestTooLarge) {
+			w.WriteHeader(http.StatusUnprocessableEntity)
 		} else if errors.Is(result.err, errArchiveFormat) {
 			w.WriteHeader(http.StatusUnsupportedMediaType)
 		} else if errors.Is(result.err, ErrArchiveTooLarge) {