- read once & read early:
  - once per batch processing
  - early (needed by metadata --harvest)

- yaml (configuration & metadata)
  site config,
  pod:
    pod.manifest,
    doc header:
      make,
      meta
- pod.manifest in yaml breaks
  - older program reading new pod and
  - newer program reading old pod
- read config first,
  - get site default language in case it is absent
    in pod.manifest
  -  ensure config is not read too many times
     (it is at present, revisit)

- yaml only: config, make & headers
  (yaml is converted directly to struct)
- toml removed: preemptively remove confusion of
  having multiple config formats
  (toml was converted to json & json to struct)
- json removed (intermediate representation):
  takes out intermediate conversion to json which
  could be attractive to have if there are
  multiple formats

- as toml alternative
- both toml & yaml (meta, conf, make) work