refactor(OAuth2)!: Rewrite auth module

[LuanRT]

What's Changed?

This is a rewrite of the OAuth2 module to address some bugs and inconsistencies. And since it changes the structure of the credentials, I'm marking this as a breaking change.

Note that you will have to update your existing credentials, that is if you wish to continue using them. Otherwise, simply delete them and sign in again.

Here's the new structure:

// NOTE: None of the optional properties are required. You can ignore them if your current credentials don't have them.

type OAuth2ClientID = {
  client_id: string;
  client_secret: string;
};

type OAuth2Tokens = {
  access_token: string;
  expiry_date: string;
  expires_in?: number;
  refresh_token: string;
  scope?: string;
  token_type?: string;
  client?: OAuth2ClientID;
};