getCredentialState abstract method
Returns the credentials state for a given user.
This method is only available on Apple platforms (which are also the only platforms where one retrieves a userIdentifier within AuthorizationCredentialAppleID instances).
The userIdentifier argument should come from a previous call to getAppleIDCredential which returned an AuthorizationCredentialAppleID.
Throws a SignInWithAppleException in case of errors, and a specific SignInWithAppleCredentialsException in case there was an error
while getting the credentials state.
Throw a SignInWithAppleNotSupportedException on unsupported platforms.
Implementation
Future<IAppleCredentialState> getCredentialState(String userIdentifier);