Tweak the ValueTransformer interface slightly to support additional
context information (to allow authenticated data to be generated by the
store and passed to the transformer). Add a prefix transformer that
looks for known matching prefixes and uses them. Add an AES GCM
transformer that performs AEAD on the values coming in and out of the
store.
Kubernetes-commit: f418468c87d3071c5d9ed14ce850996c77251080
Han Kang