[Enhancement] WebAuthenticator - Allow Parameters

[matt-goldman]

Currently when making an authentication request, the only parameters you can supply are the authentication URL and the callback URI.

I think it would be valuable to allow passing in parameters if you want to specify things like scope(s), client Id, response type etc. At the moment you may be able to get it to work by specifying these as query parameters in your authentication request URL. This is inelegant and risks overlap with the internals of this API.