Return 503 instead of crashing if upstream is down

/src/node_modules/http-proxy/lib/http-proxy/index.js:120
    throw err;
    ^

Error: connect ECONNREFUSED 10.0.233.65:80
    at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1195:16) {
  errno: -111,
  code: 'ECONNREFUSED',
  syscall: 'connect',
  address: '10.0.233.65',
  port: 80
}

Node.js v17.9.1