Allow providerParams to be a method invoked with the request

[connor4312]

This allows provideParams to be a method which, when invoked with the request object, returns query parameters to add to the request.

For certain OAuth servers which include additional metadata in the request (for us: Discord's OAuth system) it's sometimes desirable to be able to selectively request features depending on configuration in the auth request.

[ldesplat]

You're missing the documentation for the scope parameter.

Also, under Advanced Usage, would you mind adding a section describing/showing an example on how to do that for scope and providerParams.

Otherwise, it looks good to me. I was debating if we should try/catch around the user code... We could show a nice error message and throw back the original exception but I am not 100% positive that's worth it. If anybody has an opinion that it should, do speak up! :)

[ldesplat]

Hi @connor4312 This is a great contribution. Could you please document the scope parameter changes?

[connor4312]

Sorry for the delay, I've updated the documentation and added and example as requested. Let me know if there's anything else to be tweaked 😄

[ldesplat]

👍 for the example

Very nice!