[#83] services/util: Implement response service

Create response package. Implement response Service that sets values of
response meta header.

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

pkg/services/util/response/unary.go

@@ -0,0 +1,21 @@
+package response
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/util"
+	"github.com/pkg/errors"
+)
+
+// HandleUnaryRequest call passes request to handler, sets response meta header values and returns it.
+func (s *Service) HandleUnaryRequest(ctx context.Context, req interface{}, handler util.UnaryHandler) (util.ResponseMessage, error) {
+	// process request
+	resp, err := handler(ctx, req)
+	if err != nil {
+		return nil, errors.Wrap(err, "could not handle request")
+	}
+
+	setMeta(resp, s.cfg)
+
+	return resp, nil
+}