[#131] Remove metadata from Object in ListObjects

Because ListObjects v1 and v2 shouldn't show metadata. Also aws cli
doesn't show metadata even we return it.

Signed-off-by: Angira Kekteeva <kira@nspcc.ru>

api/handler/list.go

@@ -202,7 +202,6 @@ func encodeV1(arg *listObjectsArgs, list *layer.ListObjectsInfo) *ListObjectsRes
 		res.Contents = append(res.Contents, Object{
 			Key:          obj.Name,
 			Size:         obj.Size,
-			UserMetadata: obj.Headers,
 			LastModified: obj.Created.Format(time.RFC3339),
 
 			Owner: Owner{
@@ -265,7 +264,6 @@ func encodeV2(arg *listObjectsArgs, list *layer.ListObjectsInfo) *ListObjectsV2R
 		res.Contents = append(res.Contents, Object{
 			Key:          obj.Name,
 			Size:         obj.Size,
-			UserMetadata: obj.Headers,
 			LastModified: obj.Created.Format(time.RFC3339),
 
 			Owner: Owner{

api/handler/response.go

@@ -104,9 +104,6 @@ type Object struct {
 
 	// The class of storage used to store the object.
 	StorageClass string `xml:"StorageClass,omitempty"`
-
-	// UserMetadata user-defined metadata
-	UserMetadata StringMap `xml:"UserMetadata,omitempty"`
 }
 
 // ObjectVersionResponse container for object version in the response of ListBucketObjectVersionsHandler.