This allows a (more or less) arbitrary lua function to be used to load
data.
The primary advantage of this is that the size of the resulting
KeySource struct is smaller than it would be to hold the actual data
inline. It also enables the surrounding code to be slightly better
factored.
This makes it easier to compose secret management with a variety
of lua functions without having to build that directly into each
of them.
In particular: one can now use vaults or other secret stores that
we add in the future to manage credentials for HTTP clients.
Break out the KeySource object into its own reference page to
avoid manually duplicating the same information into multiple pages.
Explain how to use data fetched from eg: sqlite.
Wez Furlong
Pankaj Rathi
Cloud User
Mike Hillyer