Add does nothing for namespace subscriber, it generates cache for each of the item.

CreateGitHubSubscriber - create github subscriber with config to hub cluster, scheme of hub cluster and a syncrhonizer to local cluster.

GetDefaultSubscriber - returns the default git subscriber.

AccessToken is key of GitHub user password or personal token in secret.

Path is the key of GitHub package filter config map.

UserID is key of GitHub user ID in secret.

Subscriber - information to run namespace subscription.

SubscriberItem - defines the unit of namespace subscription.