[#1383] object: Add restrictions for Patch method

* `Patch` can't be applied for non-regular type object (tombstones,
  locks etc.)
* Complex object parts can't be patched. So, if an object has EC/Split
  header, it won't be patched.

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

pkg/services/object/patch/streamer.go

@@ -57,12 +57,31 @@ func toFullObjectHeader(hdr *objectSDK.Object) objectV2.GetHeaderPart {
 	return hs
 }
 
+func isLinkObject(hdr *objectV2.HeaderWithSignature) bool {
+	split := hdr.GetHeader().GetSplit()
+	return len(split.GetChildren()) > 0 && split.GetParent() != nil
+}
+
+func isComplexObjectPart(hdr *objectV2.HeaderWithSignature) bool {
+	return hdr.GetHeader().GetEC() != nil || hdr.GetHeader().GetSplit() != nil
+}
+
 func (s *Streamer) init(ctx context.Context, req *objectV2.PatchRequest) error {
 	hdrWithSig, addr, err := s.readHeader(ctx, req)
 	if err != nil {
 		return err
 	}
 
+	if hdrWithSig.GetHeader().GetObjectType() != objectV2.TypeRegular {
+		return errors.New("non-regular object can't be patched")
+	}
+	if isLinkObject(hdrWithSig) {
+		return errors.New("linking object can't be patched")
+	}
+	if isComplexObjectPart(hdrWithSig) {
+		return errors.New("complex object parts can't be patched")
+	}
+
 	commonPrm, err := util.CommonPrmFromV2(req)
 	if err != nil {
 		return err