Add initial controller boilerplate and example controller

Signed-off-by: Monis Khan <mok@vmware.com>

internal/controller/sync.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package controller
+
+import (
+	"context"
+
+	"k8s.io/client-go/tools/events"
+)
+
+var _ Syncer = SyncFunc(nil)
+
+type Syncer interface {
+	Sync(ctx Context) error
+}
+
+type SyncFunc func(ctx Context) error
+
+func (s SyncFunc) Sync(ctx Context) error {
+	return s(ctx)
+}
+
+type Context struct {
+	Context  context.Context
+	Name     string
+	Key      Key
+	Queue    Queue
+	Recorder events.EventRecorder
+}
+
+type Key struct {
+	Namespace string
+	Name      string
+
+	// TODO determine if it makes sense to add a field like:
+	//  Extra interface{}
+	//  This would allow a custom ParentFunc to pass extra data through to the Syncer
+	//  The boxed type would have to be comparable (i.e. usable as a map key)
+}
+
+type SyncWrapperFunc func(syncer Syncer) Syncer