[#525] event/container: Parse binary session token from Put notification

The 4th item of `Put` container notification event is a byte array of
serialized session token.

Parse session token in `ParsePut` function. Provide `Put.SessionToken`
method.

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

pkg/morph/event/container/put.go

@@ -13,6 +13,7 @@ type Put struct {
 	rawContainer []byte
 	signature    []byte
 	publicKey    []byte
+	token        []byte
 }
 
 const expectedItemNumPut = 4
@@ -29,6 +30,12 @@ func (p Put) Signature() []byte { return p.signature }
 // PublicKey of container owner.
 func (p Put) PublicKey() []byte { return p.publicKey }
 
+// Session token returns binary token of the session
+// within which the container was created.
+func (p Put) SessionToken() []byte {
+	return p.token
+}
+
 // ParsePut from notification into container event structure.
 func ParsePut(params []stackitem.Item) (event.Event, error) {
 	var (
@@ -58,5 +65,11 @@ func ParsePut(params []stackitem.Item) (event.Event, error) {
 		return nil, fmt.Errorf("could not get public key: %w", err)
 	}
 
+	// parse session token
+	ev.token, err = client.BytesFromStackItem(params[3])
+	if err != nil {
+		return nil, fmt.Errorf("could not get sesison token: %w", err)
+	}
+
 	return ev, nil
 }

pkg/morph/event/container/put_test.go

@@ -13,6 +13,7 @@ func TestParsePut(t *testing.T) {
 		containerData = []byte("containerData")
 		signature     = []byte("signature")
 		publicKey     = []byte("pubkey")
+		token         = []byte("token")
 	)
 
 	t.Run("wrong number of parameters", func(t *testing.T) {
@@ -52,12 +53,23 @@ func TestParsePut(t *testing.T) {
 		require.Error(t, err)
 	})
 
+	t.Run("wrong session token parameter", func(t *testing.T) {
+		_, err := ParsePut([]stackitem.Item{
+			stackitem.NewByteArray(containerData),
+			stackitem.NewByteArray(signature),
+			stackitem.NewByteArray(publicKey),
+			stackitem.NewMap(),
+		})
+
+		require.Error(t, err)
+	})
+
 	t.Run("correct behavior", func(t *testing.T) {
 		ev, err := ParsePut([]stackitem.Item{
 			stackitem.NewByteArray(containerData),
 			stackitem.NewByteArray(signature),
 			stackitem.NewByteArray(publicKey),
-			stackitem.NewMap(),
+			stackitem.NewByteArray(token),
 		})
 		require.NoError(t, err)
 
@@ -65,6 +77,7 @@ func TestParsePut(t *testing.T) {
 			rawContainer: containerData,
 			signature:    signature,
 			publicKey:    publicKey,
+			token:        token,
 		}, ev)
 	})
 }