Add support for authentication

[developius]

Currently if the gateway is secured via basic auth, an error is thrown. Would be good to add support for this.

From a UX perspective, I reckon this would be good:

const OpenFaaS = require('openfaas')
const openfaas = new OpenFaaS('gateway:8080', {
    user: 'admin',
    password: 'secret'
})

Not sure how this works with got, it currently throws Basic authentication must be done with auth option but I can't find documentation for that specific option.

@austinfrey I can pick this up if you want?

[austinfrey]

@developius I'm pretty sure you can just use {auth: "user:password"} in the options object. I'm thinking that anything passed into options get passed on to http.request. Let me know if that works for you.

maybe we should move towards just passing in the options {} as well instead of passing individual args. what do you think?

https://nodejs.org/dist/latest-v8.x/docs/api/http.html#http_http_request_options_callback

[austinfrey]

and we should be able to post issues on the Openfaas-incubator repo now :)

[developius]

Agreed. If we can simply pass the options through that'd be perfect, I wasn't quite sure how got was wrapping http.request but if it does that, we're good 😁

I'd say instead of having a single options object, this would be quite nice:

const openfaas = new OpenFaaS('http://gateway:8080') // check for string

const openfaas = new OpenFaaS({ // check for object
    gateway: 'http://gateway:8080'
    // etc
})

Are we able to move issues? I feel this belongs in the main repo.