issue with table to store files for multiple other tables - cakephp

Question

What I'm trying to do:
I'm using josegonzales/cakephp-upload to handle my upload by attaching an upload behaviour to a model called attachments. When I use the attachments add action there isn't any issue uploading a file but my goal is to upload a file with a hasMany relationship from Node. In The Future I'm planning to attach the AttachmentsTable to multiple other models like users for storing multiple user images.
My Setup:
Database Schema
CREATE TABLE IF NOT EXISTS `nodes` (
`id` int(10) unsigned NOT NULL,
`title` varchar(255) NOT NULL,
`body` text NOT NULL,
`created` datetime NOT NULL,
`modified` datetime NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `attachments` (
`id` int(10) unsigned NOT NULL,
`foreign_key` int(10) unsigned NOT NULL,
`model` varchar(255) NOT NULL,
`title` varchar(255) NOT NULL,
`file` varchar(255) NOT NULL,
`file_dir` varchar(255) NOT NULL,
`file_size` varchar(255) NOT NULL,
`file_type` varchar(255) NOT NULL,
`created` datetime NOT NULL,
`modified` datetime NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;
AttachmentsTable
class AttachmentsTable extends Table
{
public function initialize(array $config)
{
parent::initialize($config);
$this->table('attachments');
$this->displayField('title');
$this->primaryKey('id');
$this->addBehavior('Timestamp');
$this->addBehavior('Josegonzalez/Upload.Upload', [
'file' => [
'fields' => [
'dir' => 'file_dir',
'size' => 'file_size',
'type' => 'file_type',
],
'nameCallback' => function($data, $settings) {
$newName = uniqid() . str_replace(" ", "_", $data['name']);
return $newName;
},
'keepFilesOnDelete' => false,
'pathProcessor' => 'Josegonzalez\Upload\File\Path\DefaultProcessor',
'transformer' => 'BaseKit\Model\Table\FileTransformer',
'writer' => 'BaseKit\Model\Table\FileWriter',
],
]);
}
}
NodesTable
class NodesTable extends Table
{
public function initialize(array $config)
{
parent::initialize($config);
$this->table('nodes');
$this->displayField('title');
$this->primaryKey('id');
$this->addBehavior('Timestamp');
$this->hasMany('Attachments', [
'foreignKey' => 'foreign_key',
'conditions' => array('Attachments.model' => 'Nodes'),
'dependent' => true
]);
}
}
Nodes add.ctp
<?= $this->Form->create($node, ['type' => 'file']) ?>
<fieldset>
<legend><?= __('Add Node') ?></legend>
<?php
echo $this->Form->input('title');
echo $this->Form->input('body');
echo $this->Form->input('attachments.0.title');
echo $this->Form->input('attachments.0.file', ['type' => 'file']);
echo $this->Form->input('attachments.0.file_dir', ['type' => 'hidden']);
echo $this->Form->input('attachments.0.file_type', ['type' => 'hidden']);
echo $this->Form->input('attachments.0.file_size', ['type' => 'hidden']);
echo $this->Form->input('attachments.0.model', ['value' => 'Nodes', 'type' => 'hidden']);
?>
</fieldset>
<?= $this->Form->button(__('Submit')) ?>
<?= $this->Form->end() ?>
The Issue:
When I'm trying to upload a File using the Nodes add.ctp the file wont be uploaded and the attached uploadbehaviour won't get used. The title and model field from attachment will be saved and the foreign_key also is correctly set.
Can somebody help me and explain why the behaviour of the related attachmenttable won't be used?
If theres a major issue with my approach, how would I achieve my goal on having a flexible upload table which I can attach to any model?