Use SAM to build and deploy Lambda

[mxro]

Investigate use of AWS SAM to build and deploy lambdas. Maybe easier to develop multiple lambdas behind an API gateway (rather than the mono lambda in the current Express.js Lambda template. Will need to check how smoothly local development will still work.

SAM also recently released a new feature AWS SAM Accelerate that could be interesting to consider for development.

[mxro]

Also works in combination with CDK: Getting started with AWS SAM and the AWS CDK

Should run using Docker Running in Docker is not supported

[mxro]

Cleaning up issues.