[#263] Implement client for exchanging raw messages using gRPC protocol

Implement gRPC client that can uniformly execute any RPC on the remote
server. In the primary implementation, the client is a thin wrapper over
gRPC client connection that is required to create the client. In the future,
it is planned to expand the library with convenient functionality.

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

rpc/common/call_test.go

@@ -0,0 +1,49 @@
+package common_test
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neofs-api-go/rpc/common"
+	"github.com/stretchr/testify/require"
+)
+
+const (
+	testServiceName = "test service"
+	testRPCName     = "test RPC"
+)
+
+func TestCallMethodInfoUnary(t *testing.T) {
+	i := common.CallMethodInfoUnary(testServiceName, testRPCName)
+
+	require.Equal(t, testServiceName, i.Service)
+	require.Equal(t, testRPCName, i.Name)
+	require.False(t, i.ClientStream())
+	require.False(t, i.ServerStream())
+}
+
+func TestCallMethodInfoServerStream(t *testing.T) {
+	i := common.CallMethodInfoServerStream(testServiceName, testRPCName)
+
+	require.Equal(t, testServiceName, i.Service)
+	require.Equal(t, testRPCName, i.Name)
+	require.False(t, i.ClientStream())
+	require.True(t, i.ServerStream())
+}
+
+func TestCallMethodInfoClientStream(t *testing.T) {
+	i := common.CallMethodInfoClientStream(testServiceName, testRPCName)
+
+	require.Equal(t, testServiceName, i.Service)
+	require.Equal(t, testRPCName, i.Name)
+	require.True(t, i.ClientStream())
+	require.False(t, i.ServerStream())
+}
+
+func TestCallMethodInfoBidirectionalStream(t *testing.T) {
+	i := common.CallMethodInfoBidirectionalStream(testServiceName, testRPCName)
+
+	require.Equal(t, testServiceName, i.Service)
+	require.Equal(t, testRPCName, i.Name)
+	require.True(t, i.ClientStream())
+	require.True(t, i.ServerStream())
+}