Create detailed instructions on how to run a local testing environment

[specious]

Assemble detailed instructions on how developers can set up a local testing environment on their own systems. This should cover developers on Windows, MacOS and Linux.

• Local instances of API Gateway and Lambda can be launched with sam local
• DynamoDB can be installed and run locally
• S3 and other services can be mocked with localstack
• There are multiple ways to run Postgres with PostGIS locally, perhaps the best way being in a docker container

This will make it possible to test code locally without even having an AWS account.

[specious]

I've done some experimentation with deploying the entire stack with localstack.

Although localstack has sufficient partial support for CloudFormation to be able to deploy an entire stack to a local simulated cloud using the samlocal wrapper for sam-cli, the most prominent issue is that the free version doesn't support and will refuse to deploy:

• API Gateway V2
• Lambda layers
• RDS

The pro version which has support for those is far from free.