weapp-api/app/Models/Code.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Notifications\Notifiable;

class Code extends Model
{
    use Notifiable{
        notify as protected laravelNotify;
    }
    protected $table='code';

    public function get_user(){
        return $this->belongsTo(User::class,'user_id');
    }
    public function user(){
        return $this->belongsTo(User::class,'user_id');
    }

    public function enroll(){
        return $this->belongsTo(Code::class,'user_id','user_id');
    }

    public function notify($instance)
    {
        $this->laravelNotify($instance);
    }
}