feat: other methods to sign in than Discord

[Breakerchap]

Adding other methods to create an account would let those who don't/can't use discord be able to sign in and play.

[WolverinDEV]

Hey ho,
as this topic has been suggested multiple times and I even received a great PR (#61) I’d like to outline my thoughts in a bit more detail about this topic.

I do see a strong argument for allowing arbitrary users to sign up.
I do know, that restricting authentication to Discord introduces limitations.
However, there are several reasons why I deliberately chose this approach:

1. Account Management
   Providing native account registration introduces a number of additional challenges including credential management, account recovery, email verification, username abuse, and more.
   By relying on Discord, all of this is handled externally. This significantly reduces complexity and maintenance effort on HeXO’s side. Additionally, most users nowadays already have a Discord account, making the process convenient.

2. Preventing Spam / Bot Accounts
   As soon as a public signup form exists, it will inevitably attract bots creating accounts to post spam. I’ve seen this pattern repeatedly while administering other sites.
   Discord acts as a strong barrier here. Creating and maintaining Discord accounts is significantly more difficult than filling out a simple registration form. The same applies to users attempting to create multiple accounts (e.g., for ELO boosting) the effort is much higher when Discord is required.

3. Username Management
   I want to prevent username abuse, including impersonation.
   Tying usernames to an established identity (Discord, in this case) provides a reasonable compromise.
   This is also why changing usernames is currently not supported.

Overall, while I understand the motivation behind supporting standalone accounts, I do feel that the current Discord based approach provides strong advantages in terms of simplicity, security, and moderation. With that said, let me know how you think about it.

[Thibault-Monnier]

Couldn't the same benefits still hold if we added some other external registration methods, such as Google for example?