Omit undefined within Channels' params to fix invalid JSON serialization

[ardecvz]

• Omit undefined within Channels' params to fix invalid JSON serialization
  It's intended to mimic the ActionCable behavior when using JSON.stringify.

Projects currently migrating from the standard ActionCable client can use optional arguments when creating Channels:

// A simplified example
import { createConsumer } from '@anycable/web';

function createChannelForOnlineUsersOnPage(path, id) {
  createConsumer.subscriptions.create(
    {
      channel: 'OnlineUsersChannel',
      path: path,
      id: id,
    },
    ...
  )
}

createChannelForOnlineUsersOnPage('index')
createChannelForOnlineUsersOnPage('show', 1)

Without the change in PR, JSON is serialized incorrectly:

{"command":"subscribe","identifier":"{\"channel\":\"OnlineUsersChannel\",\"id\":undefined,\"path\":\"/index\"}}

As a result, this leads to a failure during JSON deserialization in AnyCable Go:

Command response: error_msg:"unexpected token at '{\"channel\":\"OnlineUsersChannel\",\"id\":undefined,\"path\":\"/index\"'

---

• Also, extend the type signature to allow null values.
  It's a more controversial change as type checking will no longer catch undefined and null values, but it seems that there's no limitation on the ActionCable side.
  Therefore, users can rely on passing explicit null within params (technically, it's possible to pass Objects and Arrays in JSON as well, but I'm uncertain whether allowing these two is practical too).

[palkan]

Thanks!

[palkan]

Released in @anycable/core 0.7.12