Struggling to save in 2 tables with hasOne association with cakePHP 3 - cakephp

Question

I’m struggling with the hasOne association. Here are my 2 tables :
Actually the ‘Etudiant’ (means student) has one User associated to it with the foreign key id present in both table which is the primary key of Users.
Here is the model EtudiantTable (student) :
class EtudiantTable extends Table
{
/**
* Initialize method
*
* #param array $config The configuration for the Table.
* #return void
*/
public function initialize(array $config)
{
parent::initialize($config);
$this->setTable('etudiant');
$this->setDisplayField('ETUDIANT_ID');
$this->setPrimaryKey('ETUDIANT_ID');
$this->addBehavior('Timestamp');
$this->belongsTo('Maitredestage', [
'foreignKey' => 'MAITREDESTAGE_ID',
'joinType' => 'INNER'
]);
$this->belongsToMany('Tuteuriut', [
'foreignKey' => 'ETUDIANT_ID',
'targetForeignKey' => 'TUTEURIUT_ID',
'joinTable' => 'Suivre'
]);
$this->belongsTo('Users', [
'foreignKey' => 'ID',
'joinType' => 'INNER'
]);
}
And here is the add function in the EtudiantController :
public function add()
{
$etudiant = $this->Etudiant->newEntity();
if ($this->request->is('post')) {
$etudiant = $etutable->patchEntity($etudiant, $this->request->data(), [
'associated' => ['Users']
]);
if ($this->Etudiant->save($etudiant)){
$this->Flash->success(__('The etudiant has been saved.'));
return $this->redirect(['action' => 'index']);
}
$this->Flash->error(__('The etudiant could not be saved. Please, try again.'));
}
$this->set(compact('etudiant'));
}
And my usersTable model is like this :
$this->belongsTo('Users', [ 'foreignKey' => 'ID', 'joinType' => 'INNER' ]);
I want to do this : when i insert an Etudiant it inserts a new user and both have the same id.
But currently when i insert an Etudiant i get an error saying “no default value…id is empty” but the id is supposed to be inserted automatically.
I'm completely stuck so i need your help. Thanks in advance.