Builds the schema 1 response. Every section catches its own errors and reports nil,
so one failing check never hides the others. A database that does not answer reports
database.ok: false and the status is 503.
Sections that only make sense for Rails (rails, ruby, puma, active_record_pool,
cache, actions) are omitted.
Summary
Functions
Returns {http_status, body} for the resolved config (see UpstatePhoenix.Config).