BAU: Use port health checks for API
BAU: Use port health checks for API

- We've been seeing an issue when traffic spikes of the http health
  checks taking over 1s and PaaS killing the app
- Port health checks won't care about being stuck in a queue so should
  continue to work even at high loads
- We have functional tests to catch if a deployment brings up the app
  (and so passes port health check) but then doesn't work

alphagov/notifications-api,alphagov/notifications-api