[#217] Add CORS support

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

api/layer/cors.go

@@ -0,0 +1,42 @@
+package layer
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-s3-gw/api/data"
+	"github.com/nspcc-dev/neofs-s3-gw/api/errors"
+)
+
+func (n *layer) PutBucketCORS(ctx context.Context, p *PutCORSParams) error {
+	s := &PutSystemObjectParams{
+		BktInfo:  p.BktInfo,
+		ObjName:  p.BktInfo.CORSObjectName(),
+		Metadata: map[string]string{},
+		Prefix:   "",
+		Payload:  p.CORSConfiguration,
+	}
+
+	_, err := n.putSystemObject(ctx, s)
+
+	return err
+}
+
+func (n *layer) GetBucketCORS(ctx context.Context, bktInfo *data.BucketInfo) ([]byte, error) {
+	obj, err := n.getSystemObject(ctx, bktInfo, bktInfo.CORSObjectName())
+	if err != nil {
+		if errors.IsS3Error(err, errors.ErrNoSuchKey) {
+			return nil, errors.GetAPIError(errors.ErrNoSuchCORSConfiguration)
+		}
+		return nil, err
+	}
+
+	if obj.Payload() == nil {
+		return nil, errors.GetAPIError(errors.ErrInternalError)
+	}
+
+	return obj.Payload(), nil
+}
+
+func (n *layer) DeleteBucketCORS(ctx context.Context, bktInfo *data.BucketInfo) error {
+	return n.deleteSystemObject(ctx, bktInfo, bktInfo.CORSObjectName())
+}