title: AppSync: Get user information in $context when using AWS_IAM auth
body: <p>In AppSync, when you use Cognito User Pools as your auth setting your identity you get</p>
  
  <pre><code>identity: 
     { sub: 'bcb5cd53-315a-40df-a41b-1db02a4c1bd9',
       issuer: 'https://cognito-idp.us-west-2.amazonaws.com/us-west-2_oicu812',
       username: 'skillet',
       claims: 
        { sub: 'bcb5cd53-315a-40df-a41b-1db02a4c1bd9',
          aud: '7re1oap5fhm3ngpje9r81vgpoe',
          email_verified: true,
          event_id: 'bb65ba5d-4689-11e8-bee7-2d0da8da81ab',
          token_use: 'id',
          auth_time: 1524441800,
          iss: 'https://cognito-idp.us-west-2.amazonaws.com/us-west-2_oicu812',
          'cognito:username': 'skillet',
          exp: 1524459387,
          iat: 1524455787,
          email: 'myemail@nope.com' },
       sourceIp: [ '11.222.33.200' ],
       defaultAuthStrategy: 'ALLOW',
       groups: null }
  </code></pre>
  
  <p>However when you use AWS_IAM auth you get</p>
  
  <pre><code>identity:
  { accountId: '12121212121', //&lt;--- my amazon account ID
    cognitoIdentityPoolId: 'us-west-2:39b1f3e4-330e-40f6-b738-266682302b59',
    cognitoIdentityId: 'us-west-2:a458498b-b1ac-46c1-9c5e-bf932bad0d95',
    sourceIp: [ '33.222.11.200' ],
    username: 'AROAJGBZT5A433EVW6O3Q:CognitoIdentityCredentials',
    userArn: 'arn:aws:sts::454227793445:assumed-role/MEMORYCARDS-CognitoAuthorizedRole-dev/CognitoIdentityCredentials',
    cognitoIdentityAuthType: 'authenticated',
    cognitoIdentityAuthProvider: '"cognito-idp.us-west-2.amazonaws.com/us-west-2_HighBob","cognito-idp.us-west-2.amazonaws.com/us-west-2_HighBob:CognitoSignIn:1a072f08-5c61-4c89-807e-417d22702eb7"' }
  </code></pre>
  
  <p>The Docs says that this is expected, <a href="https://docs.aws.amazon.com/appsync/latest/devguide/resolver-context-reference.html" rel="noreferrer">https://docs.aws.amazon.com/appsync/latest/devguide/resolver-context-reference.html</a> .
  However, if you use <code>AWS_IAM</code> connected to Cognito (which is required to have unauthenticated access), how are you supposed to get at the User's username, email, sub, etc?  I need access to the user's claims when using <code>AWS_IAM</code> type Auth.</p>