OptionalerrorVendor-neutral, customer-facing reason; non-null only when failed.
OptionalpreviousThe status this capability left, when it just moved.
OptionalretryWhen this capability will accept another attempt, ISO-8601 — the cooldown.
Non-null only on a failed capability whose cooldown is still in the future;
null means retry now, or that no retry will help.
One capability's state.
previousStatus,errorandretryAvailableAtappear only on the asynchronous capabilities (callon an iMessage number, andwhatsapp); a synchronous one has no transition to report and cannot fail.