[#40] morph/netmap: Implement MaxObjectSize method on wrapper

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

pkg/morph/client/netmap/wrapper/config.go

@@ -0,0 +1,29 @@
+package wrapper
+
+import (
+	"github.com/nspcc-dev/neofs-node/pkg/morph/client/netmap"
+	"github.com/pkg/errors"
+)
+
+const maxObjectSizeConfig = "MaxObjectSize"
+
+// MaxObjectSize receives max object size configuration
+// value through the Netmap contract call.
+func (w *Wrapper) MaxObjectSize() (uint64, error) {
+	args := netmap.ConfigArgs{}
+	args.SetKey([]byte(maxObjectSizeConfig))
+
+	vals, err := w.client.Config(args, netmap.IntegerAssert)
+	if err != nil {
+		return 0, errors.Wrapf(err, "(%T) could not get epoch number", w)
+	}
+
+	v := vals.Value()
+
+	sz, ok := v.(int64)
+	if !ok {
+		return 0, errors.Errorf("(%T) invalid epoch value type %T", w, v)
+	}
+
+	return uint64(sz), nil
+}