Add POC of GitHub Webhook Delivery Forwarder (#682)

* Add POC of GitHub Webhook Delivery Forwarder

* multi-forwarder and ctrl-c existing and fix for non-woring http post

* Rename source files

* Extract signal handling into a dedicated source file

* Faster ctrl-c handling

* Enable automatic creation of repo hook on startup

* Add support for forwarding org hook deliveries

* Set hook secret on hook creation via envvar (HOOK_SECRET)

* Fix org hook support

* Fix HOOK_SECRET for consistency

* Refactor to prepare for custom log position provider

* Refactor to extract inmemory log position provider

* Add configmap-based log position provider

* Rename githubwebhookdeliveryforwarder to hookdeliveryforwarder

* Refactor to rename LogPositionProvider to Checkpointer and extract ConfigMap checkpointer into a dedicated pkg

* Refactor to extract logger initialization

* Add hookdeliveryforwarder README and bump go-github to unreleased ver

pkg/hookdeliveryforwarder/configmap/config.go

@@ -0,0 +1,42 @@
+package configmap
+
+import (
+	"flag"
+	"fmt"
+
+	"github.com/go-logr/logr"
+	"k8s.io/apimachinery/pkg/runtime"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/manager"
+)
+
+type Config struct {
+	Name      string
+	Namespace string
+	Logger    logr.Logger
+	Scheme    *runtime.Scheme
+}
+
+func (c *Config) InitFlags(fs *flag.FlagSet) {
+	fs.StringVar(&c.Name, "configmap-name", "gh-webhook-forwarder", `The name of the Kubernetes ConfigMap to which store state for check-pointing.`)
+	fs.StringVar(&c.Namespace, "namespace", "default", `The Kubernetes namespace to store configmap for check-pointing.`)
+}
+
+func New(checkpointerConfig *Config) (*ConfigMapCheckpointer, manager.Manager, error) {
+	ctrl.SetLogger(checkpointerConfig.Logger)
+
+	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
+		Scheme:           checkpointerConfig.Scheme,
+		LeaderElectionID: "hookdeliveryforwarder",
+		Port:             9443,
+	})
+	if err != nil {
+		return nil, nil, fmt.Errorf("unable to start manager: %v", err)
+	}
+
+	return &ConfigMapCheckpointer{
+		Client: mgr.GetClient(),
+		Name:   checkpointerConfig.Name,
+		NS:     checkpointerConfig.Namespace,
+	}, mgr, nil
+}