[#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/service.go

@@ -0,0 +1,58 @@
+package response
+
+import (
+	"github.com/nspcc-dev/neofs-api-go/pkg"
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+	"github.com/nspcc-dev/neofs-api-go/v2/session"
+	"github.com/nspcc-dev/neofs-node/pkg/services/util"
+)
+
+// Service represents universal v2 service
+// that sets response meta header values.
+type Service struct {
+	cfg *cfg
+}
+
+// Option is an option of Service constructor.
+type Option func(*cfg)
+
+type cfg struct {
+	version *refs.Version
+
+	// TODO: neofs-node#83 add network state
+}
+
+func defaultCfg() *cfg {
+	return &cfg{
+		version: pkg.SDKVersion().ToV2(),
+	}
+}
+
+// NewService creates, initializes and returns Service instance.
+func NewService(opts ...Option) *Service {
+	c := defaultCfg()
+
+	for i := range opts {
+		opts[i](c)
+	}
+
+	return &Service{
+		cfg: c,
+	}
+}
+
+func setMeta(resp util.ResponseMessage, cfg *cfg) {
+	meta := new(session.ResponseMetaHeader)
+	meta.SetVersion(cfg.version)
+	meta.SetTTL(1) // FIXME: TTL must be calculated
+
+	// TODO: neofs-node#83
+	// meta.SetEpoch()
+
+	if origin := resp.GetMetaHeader(); origin != nil {
+		// FIXME: what if origin is set by local server?
+		meta.SetOrigin(origin)
+	}
+
+	resp.SetMetaHeader(meta)
+}