Enable switching of RedirectURI in ConfigFromJSON function about oauth2

[Koommuang7]

What version of Go are you using (go version)? - 1.21.5 What operating system and processor architecture are you using? - Mac OS 14 - ARM

What did you do?

Used oauth2 v0.15.0 for google to load my oauth2 config and exchange my code for a token. In my Google Oauth Credential I have 2 Redirect URIs set up which means that they get parsed as an array of two RedirectURIs by ConfigFromJSON

What did you expect to see?

Be able to set explicitly which RedirectURI gets loaded and returned as the config

What did you see instead?

The URL is set automatically to the first URL in the list.

RedirectURL: c.RedirectURIs[0]

It would help to have a possibility to set the wanted URL. In my example I use different redirect urls for staging, dev and prod and had invalid codes returned because the dev url was used in staging. This behavior also makes it hard to catch bugs like mine.

I'm happy to contribute a patch once we agree on the best way forward.