You need to configure the Custom Attributes within the User Pool. To achieve this, you would need to go into Cognito > UserPoolName > Sign-Up Experience > Custom attributes > Add the custom Attributes that the app requires (that Apple used to pass). These custom attributes can then be leveraged in the app client configuration.
Something important to mention, is that if you require to include these attributes in the token, you would need to create a Post-Authentication Lambda to include the required attributes within the Token being passed to the application.
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