Change underlying library for discord because it's not compliant with oauth2-client v2.x

[tristanbes]

Because the previous library is only compatible with the ultra old thephpleague/oauth2-client in version 1.x.

The documentation no longer reference the library https://github.com/teamreflex/oauth2-discord. Instead, they promote https://github.com/wohali/oauth2-discord-new.

See: http://oauth2-client.thephpleague.com/providers/thirdparty/

[bocharsky-bw]

In src/Client/Provider/DiscordClient.php the namespace of Discord\OAuth\Parts\User probably also should be updated.

[bocharsky-bw]

Should be "... require wohali/oauth2-discord-new" in the end, you changed the link URL only

[bocharsky-bw]

On one hand, it makes sense to move Discord to the OAuthClient v2, but on the other - we may provide a BC break with this PR. Probably to avoid BC breaks we need to keep both? Or, maybe a bit complicate the logic with some extra checks like if the new class from wohali/oauth2-discord-new is exist - use it, otherwise, fallback to the class from teamreflex/oauth2-discord? Anyway, I think we need to avoid bumping major version after this PR

[tristanbes]

I fixed your comments. good catch. Also, the edits from maintainers are activated if you want to provide any kind of fallbacks (which is overrated imo)

[weaverryan]

Thanks @tristanbes!

And yea, I agree - this is a small BC break, but I also really don't want to deal with fallback logic. Hopefully this type of thing will be rare.

[tristanbes]

Maybe just add it in UPGRADE or Readme to tell user that they need to require the new lib instead of the previous one. And everything will work the same ;-)

My pleasure.