stargate: migrate types (#670)

* changelog v0.4.0

* stargate: types changes

* msg and handler changes

* validation

* fixes

* more fixes

* more test fixes

* changelog

* changelog

* lint

* rm comment

* lint

* redundant if condition

types/validation_test.go

@@ -0,0 +1,55 @@
+package types
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	ethcmn "github.com/ethereum/go-ethereum/common"
+)
+
+func TestIsEmptyHash(t *testing.T) {
+	testCases := []struct {
+		name     string
+		hash     string
+		expEmpty bool
+	}{
+		{
+			"empty string", "", true,
+		},
+		{
+			"zero hash", ethcmn.Hash{}.String(), true,
+		},
+
+		{
+			"non-empty hash", ethcmn.BytesToHash([]byte{1, 2, 3, 4}).String(), false,
+		},
+	}
+
+	for _, tc := range testCases {
+		require.Equal(t, tc.expEmpty, IsEmptyHash(tc.hash), tc.name)
+	}
+}
+
+func TestIsZeroAddress(t *testing.T) {
+	testCases := []struct {
+		name     string
+		address  string
+		expEmpty bool
+	}{
+		{
+			"empty string", "", true,
+		},
+		{
+			"zero address", ethcmn.Address{}.String(), true,
+		},
+
+		{
+			"non-empty address", ethcmn.BytesToAddress([]byte{1, 2, 3, 4}).String(), false,
+		},
+	}
+
+	for _, tc := range testCases {
+		require.Equal(t, tc.expEmpty, IsZeroAddress(tc.address), tc.name)
+	}
+}