entity\user.php

<?php
namespace App\Model\Entity;

use Cake\ORM\Entity;

/**
 * User Entity.
 */
class User extends Entity
{

    /**
     * Fields that can be mass assigned using newEntity() or patchEntity().
     *
     * @var array
     */
    protected $_accessible = [
        'email' => true,
        'password' => true,
        'bookmarks' => true,
        'profile' => true,
    ];
}

table\userstable.php

<?php
namespace App\Model\Table;

use Cake\ORM\Query;
use Cake\ORM\Table;
use Cake\Validation\Validator;

/**
 * Users Model
 */
class UsersTable extends Table
{

    /**
     * Initialize method
     *
     * @param array $config The configuration for the Table.
     * @return void
     */
    public function initialize(array $config)
    {
        $this->table('users');
        $this->displayField('id');
        $this->primaryKey('id');
        $this->addBehavior('Timestamp');

        $this->hasMany('Bookmarks', [
            'foreignKey' => 'user_id',
        ]);
        $this->hasOne('Profiles', [
            'foreignKey' => 'user_id',
        ]);
    }

    /**
     * Default validation rules.
     *
     * @param \Cake\Validation\Validator $validator
     * @return \Cake\Validation\Validator
     */
    public function validationDefault(Validator $validator)
    {
        $validator
        ->add('id', 'valid', ['rule' => 'numeric'])
        ->allowEmpty('id', 'create')
        ->add('email', 'valid', ['rule' => 'email'])
        ->requirePresence('email', 'create')
        ->notEmpty('email')
        ->add('email', 'unique', ['rule' => 'validateUnique', 'provider' => 'table'])
        ->requirePresence('password', 'create')
        ->notEmpty('password')
        ->allowEmpty('dob')
        ->add('dob', 'valid', ['rule' => 'date']);

        return $validator;
    }
}