safekat/ci4/app/Models/UserModel.php

<?php

declare(strict_types=1);

namespace App\Models;

use CodeIgniter\Shield\Models\UserModel as ShieldUserModel;

class UserModel extends ShieldUserModel
{
    protected function initialize(): void
    {
        parent::initialize();

        $this->allowedFields = [
            ...$this->allowedFields,
            'first_name',   // Añadido
            'last_name',   // Añadido
        ];
    }

    protected $validationRules = [
        "username" => [
            "label" => "correo duplicado",
            "rules" => "is_unique[users.username]",
        ]

    ];

    public function getComerciales(){
        
        $builder = $this->db
            ->table("users" . " t1")
            ->select(
                "t1.id AS id, CONCAT(t1.first_name, ' ', t1.last_name) AS text"
            );

        $builder->where('t1.deleted_at', null);
        $builder->where("t2.group", "comercial");
        $builder->join("auth_groups_users t2", "t1.id = t2.user_id", "left");

        return $builder->get()->getResult();

    }
}