publicSigningKeyValue property
What publishPublicSigningKey writes: what signs for this enrollment now
plus the signing keys it has withdrawn from service, composed by
apskEntries and spelled by apskValueOf.
The same rule decides the enrollment path's apsk-versus-apskLegacy,
and the two must agree: they describe one record.
Implementation
Future<String> get publicSigningKeyValue async => apskValueOf(apskEntries(
signing: await heldSigningKeys,
withdrawn: await withdrawnSigningKeys,
authentication: await authenticationSigningKey,
));