As of Go 1.16, functionality provided in io/ioutil has been depreciated
in favour of the io or os packages. Now that Go has been
upgraded in go.mod, the linter will not pass without these changes.
This will store the secret of each LSAT minted by the proxy, which is
crucial for LSAT verification. The secrets are stored under a new
"secrets" key prefixed by the top level LSAT etcd key, and each secret
can be found by its unique identifier prefixed with the secrets key.
