CreateAndHandleReadinessLiveness creates atomic handlers for readiness and liveness, it registers them at the readyURLPath and liveURLPath and it returns a readyFn and livenessFn updater functions which can be used to set the readiness and liveness status at any time.

CreateAtomicHandler creates an atomic value handler which returns 200 OK or 503 Service Unavailable based on the state of the atomic value which defaults to initialValue.

DefaultHandler sets the Content-Type header to "application/json".

ListenAndServe creates an http.Server, sets up signal handler to listen for SIGINT and SIGTERM to perform graceful shutdown, and launches the server.