This integrates a feature that was previously reserved for enterprise
users, according to https://github.com/caddyserver/caddy/issues/2786.
The /config and /id endpoints make granular config changes possible as
well as the exporting of the current configuration.
The /load endpoint has been modified to wrap the /config handler so that
the currently-running config can always be available for export. The
difference is that /load allows configs of varying formats and converts
them using config adapters. The adapted config is then processed with
/config as JSON. The /config and /id endpoints accept only JSON.