[#140] object: Support LOCK type

Add `TypeLock` value to `Type` enum. Implement `Lock` type compatible
with corresponding message. Implement `ObjectLocked` and
`IrregularObjectLock` errors in `apistatus` package.

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

object/lock.go

@@ -0,0 +1,58 @@
+package object
+
+import (
+	v2object "github.com/nspcc-dev/neofs-api-go/v2/object"
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+	oid "github.com/nspcc-dev/neofs-sdk-go/object/id"
+)
+
+// Lock represents record with locked objects. It is compatible with
+// NeoFS API V2 protocol.
+type Lock v2object.Lock
+
+// NumberOfMembers returns number of members in lock list.
+func (x Lock) NumberOfMembers() int {
+	return (*v2object.Lock)(&x).NumberOfMembers()
+}
+
+// ReadMembers reads list of locked members.
+//
+// Buffer length must not be less than NumberOfMembers.
+func (x Lock) ReadMembers(buf []oid.ID) {
+	var i int
+
+	(*v2object.Lock)(&x).IterateMembers(func(id refs.ObjectID) {
+		buf[i] = *oid.NewIDFromV2(&id) // need smth better
+		i++
+	})
+}
+
+// WriteMembers writes list of locked members.
+func (x *Lock) WriteMembers(ids []oid.ID) {
+	var members []refs.ObjectID
+
+	if ids != nil {
+		members = make([]refs.ObjectID, len(ids))
+
+		for i := range ids {
+			members[i] = *ids[i].ToV2() // need smth better
+		}
+	}
+
+	(*v2object.Lock)(x).SetMembers(members)
+}
+
+// Marshal encodes the Lock into a NeoFS protocol binary format.
+func (x Lock) Marshal() []byte {
+	data, err := (*v2object.Lock)(&x).StableMarshal(nil)
+	if err != nil {
+		panic(err)
+	}
+
+	return data
+}
+
+// Unmarshal decodes the Lock from its NeoFS protocol binary representation.
+func (x *Lock) Unmarshal(data []byte) error {
+	return (*v2object.Lock)(x).Unmarshal(data)
+}