Auto-generate AD kerberos credential cache Secret

[sbernauer]

Basically create the Secret when the get returns a 404 in

secret-operator/rust/krb5-provision-keytab/src/credential_cache.rs

Lines 47 to 52 in a43bc97

	current_state: kube
	.get::<Secret>(&cache_ref.name, &cache_ref.namespace)
	.await
	.context(GetInitialCacheSnafu {
	cache_ref: &cache_ref,
	})?,

We have a similar mechanism to auto-create the CA cert Secret, can be copy/pasted potentially.