[#17] core/object: Implement Object and Address types

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

pkg/core/object/address.go

@@ -0,0 +1,35 @@
+package object
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+)
+
+type Address struct {
+	*object.Address
+}
+
+// MarshalStableV2 marshals Address to v2 binary format.
+func (a *Address) MarshalStableV2() ([]byte, error) {
+	if a != nil {
+		return a.ToV2().StableMarshal(nil)
+	}
+
+	return nil, nil
+}
+
+// AddressFromV2 converts v2 Address message to Address.
+func AddressFromV2(aV2 *refs.Address) (*Address, error) {
+	if aV2 == nil {
+		return nil, nil
+	}
+
+	a, err := object.AddressFromV2(aV2)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Address{
+		Address: a,
+	}, nil
+}