Welcome.php

<?php

namespace App\Mail\Trainer;

use App\I18nTrait;
use App\Model\User;
use Illuminate\Bus\Queueable;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;

/**
 * Class Welcome
 *
 * @package App\Mail\Trainer
 */
class Welcome extends Mailable
{
    use Queueable, SerializesModels, I18nTrait;

    /**
     * @var User
     */
    public $user;

    /**
     * @param User $user
     */
    public function __construct(User $user)
    {
        $this->user = $user;
    }

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        $this->setUserLocale($this->user->flag->interface_language);
        $this->subject(trans('Welcome to aerobictrainer.fitness', [], 'de'));

        return $this->view('emails.trainer.welcome-de',
            [
                'user' => $this->user,
            ]
        );
    }
}