portal-api/app/Models/ActivityLog.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class ActivityLog extends Model
{
    public $timestamps = false;

    protected $table = 'activity_logs';

    protected $fillable = [
        'log_name',
        'event',
        'description',
        'subject_type',
        'subject_id',
        'causer_type',
        'causer_id',
        'causer_name',
        'old_values',
        'new_values',
        'ip_address',
        'user_agent',
        'started_at',
        'finished_at',
        'created_at',
    ];

    protected $casts = [
        'old_values' => 'array',
        'new_values' => 'array',
        'started_at' => 'datetime:Y-m-d\TH:i:s.v\Z',
        'finished_at' => 'datetime:Y-m-d\TH:i:s.v\Z',
        'created_at' => 'datetime',
    ];

    protected static function booting(): void
    {
        static::creating(function (self $model) {
            $model->created_at ??= now();
        });
    }
}