Connect to deployed environment without redeploying

[patchwork01]

Currently the documentation says to run sleeper environment deploy to add a second user to a deployed environment. This will run cdk deploy.

The Amazon Machine Image (AMI) for the EC2 is looked up with a wildcard under Ubuntu images of a certain distribution. If a new image has been published since the last time the EC2 was deployed, the CDK will detect that the image isn't the same as what's in the EC2, and will delete and recreate the EC2.

We'd like a way to add a second user to a deployed environment without risking recreating the EC2.

One way to do that would be to get the outputs for each stack from CloudFormation rather than from the CDK. In an issue asking for a way to do this in the CDK, there's a suggestion for how to look that up in CloudFormation: aws/aws-cdk#1773 (comment)