The TES example package contains a Lambda function that, when run,
will attempt to retrieve AWS credentials. The goal of TES is to allow
users to retrieve credentials without having them hard-coded on the
system itself.

Assuming no credentials exist on the system, when the Lambda function
is run, temporary credentials will be sourced from the cloud.

The credential retrieval is retrieved with an incremental backoff
in case of an error. Users must be aware that the retrieval may not
always succeed on the first try and retry should be performed with care.

### SETUP ###
1. Copy the included index.js to your Lambda function.

2. Install aws-sdk by performing "npm install aws-sdk".

3. Unzip the Greengrass Core SDK for NodeJS into node_modules folder.

4. Zip the folder with index.js on the top level.

5. Create a Lambda in the Lambda Console.
   Handler: index.handler
   Runtime: Node.js 8.10
   Timeout: 3s
   Role: any basic execution role can be used here

6. Create a group that contains your Greengrass Core and the Lambda
function you've just created.

7. In the Greengrass console, click on the Lambda function and set
the Memory limit is at least 40MB and "Lambda lifecycle" is set to
"Make this function long-lived and keep it running indefinitely".

8. Under Settings page of the group, make sure the Group Role is
set to the role you want to use within Greengrass when
performing actions against AWS.

9. Deploy the latest Greengrass to your device.

10. Local log should display the access key, secret key and session token.