Q: How to attach Proxy-Authorization in Request Header while using Auto-Config Pac File on an iOS Device?

For example I have a http://localhost:8080/proxy.pac in which returns:

function FindProxyForURL(url, host) { return 'HTTPS localhost:443'; } 

And the request should be verified via username and password OR the basic authorization. But iOS does not prompt for credential. How do I attach credential info?