Discriminator in DiscordProvider

[mallusrgreatv2]

Goals

Add discriminator in DiscordProvider

Background

Without discriminators, many people can just impersonate others.
I know that Discord has been rolling out the new feature which removes discriminators for the past year. But the issue is, there are still a lot of accounts that have not yet converted. I personally know a couple that choose to stay with discriminators.

Proposal

https://github.com/nextauthjs/next-auth/blob/v4/packages/next-auth/src/providers/discord.ts#L40
Add discriminator option here.