Use UUIDs

[lippserd]

This is a pretty heavy change, but I think it's better to do it sooner rather than later: Kubernetes objects already provide UIDs, with most of them being UUIDs¹:

UID is a type that holds unique ID values, including UUIDs. Because we
don't ONLY use UUIDs, this is an alias to string. Being a type captures
intent and helps make sure that UIDs and names do not get conflated.

Instead of creating our IDs from namespace/name, we should simply use the Kubernetes UUIDs:

• Rename id to uuid and use github.com/google/uuid#UUID as type
• Change foreign keys accordingly
• Add uuid to schema/v1#Meta
• For related objects like containers which do not provide UIDs, we can create UUIDs like uuid.NewSHA1(PodUUID, []byte(containerName))
• Use the following code to create UUIDs from Kubernetes UIDs:

var NameSpaceKubernetes = uuid.MustParse("3f249403-2bb0-428f-8e91-504d1fd7ddb6")

func EnsureUUID(uid ktypes.UID) uuid.UUID {
	if id, err := uuid.Parse(string(uid)); err == nil {
		return id
	}

	return uuid.NewSHA1(NameSpaceKubernetes, []byte(uid))
}

Footnotes

1. types.UID ↩

[lippserd]

Implemented via #93 + Icinga/icinga-kubernetes-web#46.