03: Environment aware

Use distinct contexts for production, development and test environment
Make use of environment variables
Test suite now is completely independent of external resources (no previously running database)

Running

# development mode with hot reload enabled
npm run dev

npm run test

Make sure the database is available as described in parent README.md

Make sure the .env and .env.local environment files has proper values or the variables NODE_ENV and PG_CONNECTION_URL has valid values.