Appsync + Identity Pools + Resolver Context

The current setup we have:

• Auth0 as an openID provider. Email ID is being passed in the access token from Auth0 (Rules based setup)
• Identity Pool (authenticated only users allowed)
• Appsync with IAM based auth

We are looking to establish row level security based on the user's ID (email) but the identity value in the context for the query resolver has a value of "xxxxxxxxxxxxxx:CognitoIdentityCredentials" in the username field. How can we get the user's email into the resolver context?