Backend - make API HTTPS only

[numbleroot]

This includes:

• setting up Let's Encrypt in an automated manner (renewing of certs, copying those into docker mounted volume)
• enabling Node application to accept HTTPS calls
  • http://www.hacksparrow.com/express-js-https-server-client-example.html
  • https://stackoverflow.com/questions/11744975/enabling-https-on-express-js/11745114#11745114