[#38] service/object: Implement simplified object Head service

Implement Head service w/o linking object processing and restoration from
split-chain.

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

pkg/services/object/head/local.go

@@ -0,0 +1,24 @@
+package headsvc
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/localstore"
+	"github.com/pkg/errors"
+)
+
+type localHeader struct {
+	storage *localstore.Storage
+}
+
+func (h *localHeader) head(ctx context.Context, prm *Prm, handler func(*object.Object)) error {
+	m, err := h.storage.Head(prm.addr)
+	if err != nil {
+		return errors.Wrapf(err, "(%T) could not get header from local storage", h)
+	}
+
+	handler(m.Head())
+
+	return nil
+}