Verifies an Apple App Attest attestation object, following Apple's validation steps 1-9.
keyId and attestation (base64 or base64url) and nonce (the challenge string)
keyId
attestation
nonce
{ ok, jwk, alg, appId, environment, attestation }, or a refusal
{ ok, jwk, alg, appId, environment, attestation }
Verifies an Apple App Attest attestation object, following Apple's validation steps 1-9.