b2: use file id from listing when not presented in headers

backend/b2/b2.go

@@ -1883,9 +1883,14 @@ func (o *Object) getOrHead(ctx context.Context, method string, options []fs.Open
 	// --b2-download-url cloudflare strips the Content-Length
 	// headers (presumably so it can inject stuff) so use the old
 	// length read from the listing.
+	// Additionally, the official examples return S3 headers
+	// instead of native, i.e. no file ID, use ones from listing.
 	if info.Size < 0 {
 		info.Size = o.size
 	}
+	if info.ID == "" {
+		info.ID = o.id
+	}
 	return resp, info, nil
 }