[#168] refs: Implement binary/JSON encoders/decoders on Signature

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

pkg/signature_test.go

@@ -0,0 +1,33 @@
+package pkg
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSignatureEncoding(t *testing.T) {
+	s := NewSignature()
+	s.SetKey([]byte("key"))
+	s.SetSign([]byte("sign"))
+
+	t.Run("binary", func(t *testing.T) {
+		data, err := s.Marshal()
+		require.NoError(t, err)
+
+		s2 := NewSignature()
+		require.NoError(t, s2.Unmarshal(data))
+
+		require.Equal(t, s, s2)
+	})
+
+	t.Run("json", func(t *testing.T) {
+		data, err := s.MarshalJSON()
+		require.NoError(t, err)
+
+		s2 := NewSignature()
+		require.NoError(t, s2.UnmarshalJSON(data))
+
+		require.Equal(t, s, s2)
+	})
+}