feat: fixing informer issues (#191)

This completely reimplements the informer system. 
It now avoids the issues using the cache informer watcher which
occasionally ommits errors - to my best reckoning it is due to partial
object updates not deserialising properly.

Signed-off-by: Alex Jones <alexsimonjones@gmail.com>

go.sum

@@ -53,6 +53,7 @@ github.com/bufbuild/connect-go v0.5.0 h1:JFbWPWpasBqzM5h/awoRhAXmLERZQlQ5xTn42uf
 github.com/bufbuild/connect-go v0.5.0/go.mod h1:ZEtBnQ7J/m7bvWOW+H8T/+hKQCzPVfhhhICuvtcnjlI=
 github.com/buger/jsonparser v1.1.1/go.mod h1:6RYKKt7H4d4+iWqouImQ9R2FZql3VbhNgx27UK13J/0=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
+github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cespare/xxhash/v2 v2.1.1/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cespare/xxhash/v2 v2.1.2 h1:YRXhKfTDauu4ajMg1TPgFO5jnlC2HCbmLXMcTG5cbYE=

pkg/sync/kubernetes/ffclientset.go

@@ -0,0 +1,113 @@
+package kubernetes
+
+import (
+	"context"
+	"errors"
+
+	"github.com/open-feature/open-feature-operator/apis/core/v1alpha1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apimachinery/pkg/watch"
+	"k8s.io/client-go/kubernetes/scheme"
+	"k8s.io/client-go/rest"
+)
+
+type ClientInterface interface {
+	List(opts metav1.ListOptions) (*v1alpha1.FeatureFlagConfigurationList, error)
+	Get(name string, options metav1.GetOptions) (*v1alpha1.FeatureFlagConfiguration, error)
+	Create(*v1alpha1.FeatureFlagConfiguration) (*v1alpha1.FeatureFlagConfiguration, error)
+	Watch(opts metav1.ListOptions) (watch.Interface, error)
+}
+
+type FeatureFlagConfigurationInterface interface {
+	FeatureFlagConfigurations(namespace string) ClientInterface
+}
+
+type FeatureFlagConfigurationImpl struct {
+	restClient rest.Interface
+	ns         string
+}
+
+type FeatureFlagConfigurationRestClient struct {
+	restClient rest.Interface
+}
+
+func (c *FeatureFlagConfigurationImpl) List(opts metav1.ListOptions) (*v1alpha1.FeatureFlagConfigurationList, error) {
+	result := v1alpha1.FeatureFlagConfigurationList{}
+	err := c.restClient.
+		Get().
+		Resource(featureFlagConfigurationName).
+		Do(context.Background()).
+		Into(&result)
+
+	return &result, err
+}
+
+func (c *FeatureFlagConfigurationImpl) Get(name string,
+	opts metav1.GetOptions,
+) (*v1alpha1.FeatureFlagConfiguration, error) {
+	result := v1alpha1.FeatureFlagConfiguration{}
+	err := c.restClient.
+		Get().
+		Namespace(c.ns).
+		Resource(featureFlagConfigurationName).
+		Name(name).
+		VersionedParams(&opts, scheme.ParameterCodec).
+		Do(context.Background()).
+		Into(&result)
+
+	return &result, err
+}
+
+func (c *FeatureFlagConfigurationImpl) Create(project *v1alpha1.FeatureFlagConfiguration) (*v1alpha1.
+	FeatureFlagConfiguration, error,
+) {
+	result := v1alpha1.FeatureFlagConfiguration{}
+	err := c.restClient.
+		Post().
+		Namespace(c.ns).
+		Resource(featureFlagConfigurationName).
+		Body(project).
+		Do(context.Background()).
+		Into(&result)
+
+	return &result, err
+}
+
+func (c *FeatureFlagConfigurationImpl) Watch(opts metav1.ListOptions) (watch.Interface, error) {
+	opts.Watch = true
+	return c.restClient.
+		Get().
+		Namespace(c.ns).
+		Resource(featureFlagConfigurationName).
+		VersionedParams(&opts, scheme.ParameterCodec).
+		Watch(context.Background())
+}
+
+func NewForConfig(config *rest.Config) (*FeatureFlagConfigurationRestClient, error) {
+	if config == nil {
+		return nil, errors.New("rest config is nil")
+	}
+	config.ContentConfig.GroupVersion = &schema.
+		GroupVersion{
+		Group:   v1alpha1.GroupVersion.Group,
+		Version: v1alpha1.GroupVersion.Version,
+	}
+	config.APIPath = "/apis"
+	config.UserAgent = rest.DefaultKubernetesUserAgent()
+	config.NegotiatedSerializer = serializer.NewCodecFactory(scheme.Scheme)
+	client, err := rest.RESTClientFor(config)
+	if err != nil {
+		return nil, err
+	}
+
+	return &FeatureFlagConfigurationRestClient{restClient: client}, nil
+}
+
+func (c *FeatureFlagConfigurationRestClient) FeatureFlagConfigurations(namespace string) ClientInterface {
+	return &FeatureFlagConfigurationImpl{
+		restClient: c.restClient,
+		ns:         namespace,
+	}
+}