eCert-MBIP/app/Models/AuditLog.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class AuditLog extends Model
{
    protected $fillable = [
        'user_id', 'action', 'auditable_type', 'auditable_id',
        'old_values', 'new_values', 'ip_address', 'user_agent',
    ];

    protected function casts(): array
    {
        return [
            'old_values' => 'array',
            'new_values' => 'array',
        ];
    }

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

    public function auditable()
    {
        return $this->morphTo();
    }
}