invoiceninja/app/Http/ValidationRules/Ninja/CanAddUserRule.php

<?php
/**
 * Invoice Ninja (https://invoiceninja.com).
 *
 * @link https://github.com/invoiceninja/invoiceninja source repository
 *
 * @copyright Copyright (c) 2021. Invoice Ninja LLC (https://invoiceninja.com)
 *
 * @license https://www.elastic.co/licensing/elastic-license
 */

namespace App\Http\ValidationRules\Ninja;

use App\Models\CompanyUser;
use App\Models\User;
use Illuminate\Contracts\Validation\Rule;

/**
 * Class CanAddUserRule.
 */
class CanAddUserRule implements Rule
{

    public function __construct()
    {
    }

    /**
     * @param string $attribute
     * @param mixed $value
     * @return bool
     */
    public function passes($attribute, $value)
    {

        // $count = CompanyUser::query()
        //     ->with('user')
        //     ->where('account_id', auth()->user()->account_id)
        //     ->distinct()
        //     ->select('user_id')
        //     ->count(); 


        $count = User::query()
            ->with(['company_user' => function ($query){
              return $query->whereNull('company_user.deleted_at');
            }])
            ->where('account_id', auth()->user()->account_id)
            ->distinct()
            ->select('users.id')
            ->count();

        return $count < auth()->user()->company()->account->num_users;
        //return auth()->user()->company()->account->users->count() < auth()->user()->company()->account->num_users;
    }

    /**
     * @return string
     */
    public function message()
    {
        return ctrans('texts.limit_users', ['limit' => auth()->user()->company()->account->num_users]);
    }
}