fix(client): support custom negotiated serializer

The Kubernetes client allows for users to configure a serializer which
is used to encode and decode resources exchanged with the Kubernetes API
server.

This changeset modifies the controller-runtime client to only set the
default serializer if the NegotiatedSerializer option is nil.

Signed-off-by: Terin Stock <terin@cloudflare.com>

pkg/client/apiutil/apimachinery.go

@@ -69,7 +69,9 @@ func GVKForObject(obj runtime.Object, scheme *runtime.Scheme) (schema.GroupVersi
 // with the given GroupVersionKind.
 func RESTClientForGVK(gvk schema.GroupVersionKind, baseConfig *rest.Config, codecs serializer.CodecFactory) (rest.Interface, error) {
 	cfg := createRestConfig(gvk, baseConfig)
-	cfg.NegotiatedSerializer = serializer.DirectCodecFactory{CodecFactory: codecs}
+	if cfg.NegotiatedSerializer == nil {
+		cfg.NegotiatedSerializer = serializer.DirectCodecFactory{CodecFactory: codecs}
+	}
 	return rest.RESTClientFor(cfg)
 }