Allow additional attributes on the turbo_stream_action_tag helper

[marcoroth]

Turbo now supports Custom Stream Actions via hotwired/turbo#479. In order to be able to properly use Custom Stream Actions in your application you also need to have a new server-side helper to generate the corresponding <turbo-stream> element.

Imagine a Custom Stream Action console_log which prints out a message via JavaScript's console.log. The action takes two arguments: the first one is the message itself and the second optional argument is the log-level.

import { StreamActions } from '@hotwired/turbo'

StreamActions.console_log = function () {
  const level = this.getAttribute('level') || 'log'
  const message = this.getAttribute('message')

  console[level](message)
}

This Pull Requests allows to write a custom helper, like so:

# app/helpers/custom_stream_helper.rb

module CustomStreamHelper
  def console_log(message, level = :log)
    turbo_stream_action_tag :console_log, target: "body", message: message, level: level
  end
end

Turbo::Streams::TagBuilder.prepend(CustomStreamHelper)

This now allows you to call console_log on turbo_stream throughout the application with:

turbo_stream.console_log "Hello World"

Which produces the following payload:

<turbo-stream message="Hello World" level="log" action="console_log" target="body"><template></template></turbo-stream>

Previously this wasn't possible because the turbo_stream_action_tag method wouldn't take any additional arguments.