When an envelope transformer calls out to KMS (for instance), it will be
very helpful to pass a `context.Context` to allow for cancellation. This
patch does that, while passing the previously-expected additional data
via a context value.
Signed-off-by: Steve Kuznetsov <skuznets@redhat.com>
Kubernetes-commit: 27312feb9983c18d1daf00afba788727d024cdd0
Steve Kuznetsov
haoshuwei
Yang Li
Slava Semushin
Clayton Coleman