[#64] core/object: Implement tombstone content messages

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

pkg/core/object/tombstone_test.go

@@ -0,0 +1,43 @@
+package object
+
+import (
+	"crypto/sha256"
+	"testing"
+
+	"github.com/nspcc-dev/neofs-api-go/pkg/container"
+	"github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTombstoneContent_MarshalBinary(t *testing.T) {
+	cid1 := container.NewID()
+	cid1.SetSHA256([sha256.Size]byte{1, 2})
+
+	id1 := object.NewID()
+	id1.SetSHA256([sha256.Size]byte{3, 4})
+
+	addr1 := object.NewAddress()
+	addr1.SetObjectID(id1)
+	addr1.SetContainerID(cid1)
+
+	cid2 := container.NewID()
+	cid2.SetSHA256([sha256.Size]byte{5, 6})
+
+	id2 := object.NewID()
+	id2.SetSHA256([sha256.Size]byte{7, 8})
+
+	addr2 := object.NewAddress()
+	addr2.SetObjectID(id2)
+	addr2.SetContainerID(cid2)
+
+	c := NewTombstoneContent()
+	c.SetAddressList(addr1, addr2)
+
+	data, err := c.MarshalBinary()
+	require.NoError(t, err)
+
+	c2, err := TombstoneContentFromBytes(data)
+	require.NoError(t, err)
+
+	require.Equal(t, c, c2)
+}