[#58] object/delete: Process linking object in Delete service

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

pkg/services/object/head/relation.go

@@ -0,0 +1,40 @@
+package headsvc
+
+import (
+	"context"
+
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/pkg/errors"
+)
+
+type RelationHeader struct {
+	srch RelationSearcher
+
+	svc *Service
+}
+
+func NewRelationHeader(srch RelationSearcher, svc *Service) *RelationHeader {
+	return &RelationHeader{
+		srch: srch,
+		svc:  svc,
+	}
+}
+
+func (h *RelationHeader) HeadRelation(ctx context.Context, addr *objectSDK.Address) (*object.Object, error) {
+	id, err := h.srch.SearchRelation(ctx, addr)
+	if err != nil {
+		return nil, errors.Wrapf(err, "(%T) could not find relation", h)
+	}
+
+	a := objectSDK.NewAddress()
+	a.SetContainerID(addr.GetContainerID())
+	a.SetObjectID(id)
+
+	r, err := h.svc.Head(ctx, new(Prm).WithAddress(a))
+	if err != nil {
+		return nil, errors.Wrapf(err, "(%T) could not receive relation header", h)
+	}
+
+	return r.Header(), nil
+}