Add in API for Kick

[azgoodaz]

While some don't like the service, Kick is growing and I think this program would be beneficial for multi-streaming so that the streamer or even user can see both chats at the same time.

[iProdigy]

See #4676 (comment)

[Nerixyz]

While the linked issue just says "we won't do this", I'll try to give a bit more context.

Kick does not provide a public API that we can use to read and send messages. You might've seen the API at https://docs.kick.com/. This API does not provide enough functionality for us. There are two major reasons:

1. We can't read chat. The events they provide can only be received by webhooks. Webhooks require a server, so we can't use them as a client. Websocket-based events KickEngineering/KickDevDocs#20 proposes WebSocket events. It's open for almost a year.
2. We can't authorize the user (while providing a decent user experience). Kick only provides the Authorization Grant OAuth flow to get a user token¹. This flow needs a client secret. We can't ship this with Chatterino, because the client secret allows anyone to create an App Access Token. That is not as powerful as on Twitch, but you can read moderation events with it, and we don't know what APIs will be added in the future. The proper way to use the Authorization Grant flow is with a trusted server. The server now sees all tokens and stores the client secret. Chatterino should also work without services other than the main platform (Twitch/Kick in this case). The only option I see is to ask the user for a client ID and secret (i.e. ask each user to create a separate app). Something like the OAuth Device Authorization flow has been requested (Authorization Grant flow, these are missing: *Devices Code || Qr-Code*, TVs, Box Tvs, rasp pi KickEngineering/KickDevDocs#111), but nothing has happened since.

If you only care about reading chat, then you can also use the private API. While this will likely never be added to Chatterino itself, you can use that API in plugins. You can use the private API there today and read messages. However, the Chatterino messages you can create with plugins can't show emotes yet. It's no secret that I've been working on improving plugin support, but that takes time. With improved plugin support, you could also read/write chat from other platforms like YouTube.

Footnotes

1. Technically it also has the Implicit Grant flow, but the tokens only last an hour with no way to refresh them. ↩