gistfile1.php

#
# ClientsController
#
    public function add()
    {
    	$client = $this->Clients->newEntity();
    	  
    	if ($this->request->is('post')) {
    		$this->request->data['user'] = [ 'username' => 'teste', 'password' => 'teste' ];
    		debug($this->request->data);
    		$client = $this->Clients->newEntity($this->request->data, [
    				'associated' => [ 'Users' ]
    		]);
  
    		if ($this->Clients->save($client)) {
    			$this->Flash->success('The client has been saved.');
    			return $this->redirect(['action' => 'index']);
    		} else {
    			$this->Flash->error('The client could not be saved. Please, try again.');
    		}
    	}
    	
    	$regions = $this->getRegions();
    	
    	$this->set(compact('client', 'regions'));
    	$this->set('_serialize', ['client']);
    	
    }
    
#
# ClientsTable
#
<?php
namespace App\Model\Table;

use App\Model\Entity\Client;
use Cake\ORM\Query;
use Cake\ORM\RulesChecker;
use Cake\ORM\Table;
use Cake\Validation\Validator;

/**
 * Clients Model
 */
class ClientsTable extends Table
{

    /**
     * Initialize method
     *
     * @param array $config The configuration for the Table.
     * @return void
     */
    public function initialize(array $config)
    {
        $this->table('clients');
        $this->displayField('id');
        $this->primaryKey('id');
        $this->addBehavior('Timestamp');
        $this->hasOne('Users', [
            'foreignKey' => 'users_id',
        	'dependent' => true
        ]);
    }

    /**
     * Default validation rules.
     *
     * @param \Cake\Validation\Validator $validator Validator instance.
     * @return \Cake\Validation\Validator
     */
    public function validationDefault(Validator $validator)
    {
        $validator
            ->add('id', 'valid', ['rule' => 'numeric'])
            ->allowEmpty('id', 'create')
            ->requirePresence('cnpj', 'create')
            ->notEmpty('cnpj')
            ->requirePresence('razao_social', 'create')
            ->notEmpty('razao_social')
            ->add('region', 'valid', ['rule' => 'numeric'])
            ->requirePresence('region', 'create')
            ->notEmpty('region')
            ->add('is_salesman', 'valid', ['rule' => 'numeric'])
            ->allowEmpty('is_salesman')
            ->allowEmpty('salesman')
            ->allowEmpty('contact_name')
            ->add('email', 'valid', ['rule' => 'email'])
            ->allowEmpty('email')
            ->allowEmpty('phone_number');

        return $validator;
    }

    /**
     * Returns a rules checker object that will be used for validating
     * application integrity.
     *
     * @param \Cake\ORM\RulesChecker $rules The rules object to be modified.
     * @return \Cake\ORM\RulesChecker
     */
    public function buildRules(RulesChecker $rules)
    {
        $rules->add($rules->isUnique(['email']));
        $rules->add($rules->existsIn(['users_id'], 'Users'));
        return $rules;
    }
}