InitFromCtrl initializes within a controller.

InitFromEnv initializes a backend looking into Env for config data.

Instantiate instantiates a Backend of type `backendType`.

Register registers a new backend type with name `name`staging function is a function that returns a backend of that type.

Functions is a map of labelled functions that return secret backend instances.

Instances are instantiated secret backends.

Backend is an abstract backend interface.