Expose raw fetch response

[djlauk]

I need to get the raw response from the data API web service in order to further work with it myself. I.e. for this use case I do not want the return value of response.json(), as in my current use case I'll need to call reponse.blob().

I think returning the raw response object, if requested through an extra parameter, will provide maximum flexibility. Adding a parameter with a default value would provide backwards compatibility with existing client code.