[#170] Support tar.gz exploding

During upload if "X-Attribute-Explode-Archive" is set, gate tries to read tar.gz archive and creates an object for each file. Each object acquires a FilePath attribute which is calculated relative to the archive root

Signed-off-by: Nikita Zinkevich <n.zinkevich@yadro.com>

internal/handler/filter.go

@@ -39,7 +39,7 @@ func filterHeaders(l *zap.Logger, header *fasthttp.RequestHeader) (map[string]st
 		// check if key gets duplicated
 		// return error containing full key name (with prefix)
 		if _, ok := result[string(clearKey)]; ok {
-			err = fmt.Errorf("key duplication error: %s", string(key))
+			err = fmt.Errorf("header key duplication error: %s", string(key))
 			return
 		}