// config/rocket-chat.php
...
    /*
    |--------------------------------------------------------------------------
    | Default RocketChat Connection Name
    |--------------------------------------------------------------------------
    |
    | Here you may specify which RocketChat connections below you wish
    | to use as your default connection for all RocketChat notifications. Of course
    | you may use many connections at once using the RocketChat static methods or 
    | RocketChatMessage connection method.
    |
    */

    'default' => env('ROCKETCHAT_CONNECTION', 'rocket-chat'),

    /*
    |--------------------------------------------------------------------------
    | RocketChat Connections
    |--------------------------------------------------------------------------
    |
    | Here are each of the RocketChat connections setup for your application.
    |
    */

    'connections' => [

        'rocket-chat' => [
            // Base URL for RocketChat API server (https://your.rocketchat.server.com)
            'url' => env('ROCKETCHAT_URL'),
            'token' => env('ROCKETCHAT_TOKEN'),
            'user_id' => env('ROCKETCHAT_USER_ID')
        ]

    ]
...

use Illuminate\Notifications\Notification;
use TeamNiftyGmbh\RocketChatNotifications\Channels\RocketChatNotificationChannel;
use TeamNiftyGmbh\RocketChatNotifications\Messages\RocketChatMessage;

class TaskCompleted extends Notification
{
    public function via(mixed $notifiable): array
    {
        return [
            RocketChatNotificationChannel::class
        ];
    }

    public function toRocketChat($notifiable): RocketChatMessage
    {
        return RocketChatMessage::create('Test Message');
    }
}

public function routeNotificationForRocketChat(): string
{
    return 'channel_name';
}

public function toRocketChat($notifiable)
{
    return RocketChatMessage::create('Test message')
        ->connection('rocket-chat') // optional to alter the default connection, overrides 'domain', 'to' and 'from'
        ->domain('https://your.rocketchat.server.com') //optional if set in config
        ->to('channel_name') // optional if set in config
        ->from('access_token', 'rocket_chat_user_id') // optional if set in config
        ->attachments([
            RocketChatAttachment::create()->imageUrl('test'),
            RocketChatAttachment::create(['image_url' => 'test']),
            new RocketChatAttachment(['image_url' => 'test']),
            [
                'image_url' => 'test'
            ]   
        ]);   
}

[
    [
        'short' => false, // Whether this field should be a short field. Default: false
        'title' => 'Title 1', //The title of this field. Required
        'value' => 'Value 1' // The value of this field, displayed underneath the title value. Required
    ],
    [
        'short' => true,
        'title' => 'Title 2',
        'value' => 'Value 2'
    ],

];   

use TeamNiftyGmbh\RocketChatNotifications\Messages\RocketChatMessage;
use TeamNiftyGmbh\RocketChatNotifications\RocketChat

RocketChat::send('domain', 'token', 'userId', 'channel', RocketChatMessage::create('message'));

use TeamNiftyGmbh\RocketChatNotifications\Messages\RocketChatMessage;
use TeamNiftyGmbh\RocketChatNotifications\RocketChat

RocketChat::sendVia('connection', 'channel', RocketChatMessage::create('message'));