Add v2 version to go module name

Replace all elements from `v2` to root directory.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

storagegroup/marshal.go

@@ -0,0 +1,78 @@
+package storagegroup
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+	"github.com/nspcc-dev/neofs-api-go/v2/rpc/message"
+	storagegroup "github.com/nspcc-dev/neofs-api-go/v2/storagegroup/grpc"
+	"github.com/nspcc-dev/neofs-api-go/v2/util/proto"
+)
+
+const (
+	sizeField       = 1
+	hashField       = 2
+	expirationField = 3
+	objectIDsField  = 4
+)
+
+// StableMarshal marshals unified storage group structure in a protobuf
+// compatible way without field order shuffle.
+func (s *StorageGroup) StableMarshal(buf []byte) ([]byte, error) {
+	if s == nil {
+		return []byte{}, nil
+	}
+
+	if buf == nil {
+		buf = make([]byte, s.StableSize())
+	}
+
+	var (
+		offset, n int
+		err       error
+	)
+
+	n, err = proto.UInt64Marshal(sizeField, buf[offset:], s.size)
+	if err != nil {
+		return nil, err
+	}
+
+	offset += n
+
+	n, err = proto.NestedStructureMarshal(hashField, buf[offset:], s.hash)
+	if err != nil {
+		return nil, err
+	}
+
+	offset += n
+
+	n, err = proto.UInt64Marshal(expirationField, buf[offset:], s.exp)
+	if err != nil {
+		return nil, err
+	}
+
+	offset += n
+
+	_, err = refs.ObjectIDNestedListMarshal(objectIDsField, buf[offset:], s.members)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf, nil
+}
+
+// StableSize of storage group structure marshalled by StableMarshal function.
+func (s *StorageGroup) StableSize() (size int) {
+	if s == nil {
+		return 0
+	}
+
+	size += proto.UInt64Size(sizeField, s.size)
+	size += proto.NestedStructureSize(hashField, s.hash)
+	size += proto.UInt64Size(expirationField, s.exp)
+	size += refs.ObjectIDNestedListSize(objectIDsField, s.members)
+
+	return size
+}
+
+func (s *StorageGroup) Unmarshal(data []byte) error {
+	return message.Unmarshal(s, data, new(storagegroup.StorageGroup))
+}