[#283] pkg/owner: Implement generators of ID's for testing

Create `ownertest` package with functions which generate random `owner.ID`
instances. These functions is going to be used for testing.

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

pkg/owner/test/id.go

@@ -0,0 +1,27 @@
+package ownertest
+
+import (
+	"math/rand"
+
+	"github.com/nspcc-dev/neofs-api-go/pkg/owner"
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
+)
+
+// Generate returns owner.ID calculated
+// from a random owner.NEO3Wallet.
+func Generate() *owner.ID {
+	data := make([]byte, owner.NEO3WalletSize)
+
+	rand.Read(data)
+
+	return GenerateFromBytes(data)
+}
+
+// GenerateFromBytes returns owner.ID generated
+// from a passed byte slice.
+func GenerateFromBytes(val []byte) *owner.ID {
+	idV2 := new(refs.OwnerID)
+	idV2.SetValue(val)
+
+	return owner.NewIDFromV2(idV2)
+}