Fixed channels HTTP API endpoint

[Catzilla]

Fixes #149

Currently, we can only get presence channels, because there is a filter in code:

laravel-websockets/src/HttpApi/Controllers/FetchChannelsController.php

Lines 14 to 16 in 1c2b89b

	$channels = Collection::make($this->channelManager->getChannels($request->appId))->filter(function ($channel) {
	return $channel instanceof PresenceChannel;
	});

But according to Pusher API documentation, there is no limitations needed, and presence channels should be filtered using filter_by_prefix=presence-:

https://pusher.com/docs/rest_api#method-get-channels

In this pull request, I implemented correct behavior for this endpoint:

• List with all channels now returned
• Attribute user_count must be requested via info query param
• Error code 400 will be returned if user_count is requested, and the request is not limited to presence channels

[francislavoie]

Looks like the pusher docs URLs have changed. The new URL is https://pusher.com/docs/channels/library_auth_reference/rest-api#get-channels-fetch-info-for-multiple-channels-

[mpociot]

Thank you!