Allow passing more options to fetch

[jovinbm]

First, thank you for the awesome work!

Currently the library seems to be only pass the headers option to fetch whilst fetch takes many more options like

fetch('https://example.com', {
  credentials: 'include'  
})

I'm not that familiar with typescript to make a quick pull request without messing things up, but perhaps keeping all the passed in options at https://github.com/graphcool/graphql-request/blob/master/src/index.ts#L18 and something like

const response = await fetch(this.url, Object.assign({}, this.options, {
      method: 'POST',
      headers: Object.assign({'Content-Type': 'application/json'}, this.options.headers),
      body,
    }))

at https://github.com/graphcool/graphql-request/blob/master/src/index.ts#L30.

[schickling]

The idea looks reasonable, however I wonder how to deal with the body property in particular.

@IvanGoncharov @RomanGotsiy any feedback here?

[RomanHotsiy]

@schickling this sounds reasonable.
Regarding body property, I would just ignore it (especially since options can be used to init client instance and body doesn't make sense here). I would also not include body in typescript typing for Options so typescript users will be notified that body property is not expected.

Something like this:

const response = await fetch(this.url, {
  method: 'POST',
  ...this.options, // to allow overwrite method but merge headers and ignore body
  headers: Object.assign({'Content-Type': 'application/json'}, this.options.headers),
  body,
})

[schickling]

Sounds good! Does somebody want to create a PR + some tests for this?

[RomanHotsiy]

I can make a PR on weekends if nobody creates it earlier