Auto-append params and post body values from config

[beriberikix]

The FR is for auth in mind. Most APIs that use authentication require you to append a token on every request either as a query param or in the post body. Setting that to a variable in the config object would be super convienient for calling an api behind oauth2.

[mlouro]

@beriberikix thanks for the feedback, it's definitely something that should (and will) be covered.