Appsync GraphQL with Cognito Identity Pool Federation

Hi,

I have setup AppSync GraphQL with IAM auth, and using Cognito Id Pool together with the Identity Pool, have successfully obtained AccessKey/SecretKey/Session Token. With these credentials, I can also Mutate the GraphQL API. I have been using Postman to to this mutation, using AWS Signature setting in postman to call the GraphQL Api Url, and posting the mutation. Everything is working and the mutation is able to be saved into DynamoDB.

HOWEVER.... I've been searching for a while as to why the postman POST request is not forwarding the context.identity object. The CloudWatch log for the GraphQL mutation call contains the arguments object inside the context key, but there is no "identity" field anywhere in the payload.

Have I missed any setting or not provide something at the client (postman) side such that the identity is not forwarded?