Add protocol 3

[privorotskii]

I've made a draft for #9, but there are several questions:

1. UnauthorizedError is currently sent as ['unauthorized', message], is it needed to be sent with meta.id too, as ['unauthorized', meta.id, message]?
2. UnknownActionError or UnknownChannelError are now ['unknownChannel', meta.id]. Should it be unified to ['unknownChannel', meta.id, stack]?
3. This question may be silly, but how is it supposed to answer with a 500 HTTP code, while it communicates via WebSockets and not HTTP? Should the 500 code be placed in the answer's body somehow?

[ai]

['unauthorized', message]

There is no unauthorized answer in Logux Back-end Protocol.

If Rails developer didn’t provide auth callback, the Rails app should throw an error during the start.

['unknownChannel', meta.id, stack]

You do not need stack for an unknown channel. It is not an error. You just do not have a processor for the channel name. You do not need a stack.

This question may be silly, but how is it supposed to answer with a 500 HTTP code, while it communicates via WebSockets and not HTTP?

Logux Back-end Protocol (HTTP-protocol between Logux Server and Rails server) doesn’t use HTTP statuses because of patching. Logux Server send many different actions to the Rails and HTTP statuses will not work if you have an error in one action and successfuly processed other actions.