Get address requirements for a country

Whether an address in country carries a state / region and a postal code, so a form can be shaped and validated before the profile is submitted. Values reflect the country's national address format: required must be sent, optional is accepted but never blocks, and absent means the country's format has no such field — omit it rather than sending an empty string. Requirements are country-scoped, not org-scoped, so the response is identical for every caller — this endpoint needs no authentication.