The identity field varies based on the authentication type used for the AppSync API.
When using an API key, it will be null. When using IAM, it will contain the AWS credentials of the user. When using Cognito,
it will contain the Cognito user pool information. When using a Lambda authorizer, it will contain the information returned
by the authorizer.
Event type for AppSync Events.
For strongly typed validation and parsing at runtime, check out the
@aws-lambda-powertools/parserpackage.