title: Magento add Customer Select in Customer Info
body: <p>I need to create a customer attribute callend "parent_id". 
  A customer "child" need to have a "customer parent", so, I want to put a select of customers in customer info to choice a customer parent to a customer child . OMG </p>
  
  <p>I tried this: </p>
  
  <p>In Xkey/Usuarios/sql/mysql4-install-0.1.0.php </p>
  
  <pre><code>$setup = Mage::getModel('customer/entity_setup', 'core_setup');
      $setup-&gt;addAttribute('customer', 'parent_id', array(
          'type' =&gt; 'int',
      'input' =&gt; 'select',
      'label' =&gt; 'Customer Parent Id',
      'global' =&gt; 1,
      'visible' =&gt; 1,
      'required' =&gt; 1,
      'user_defined' =&gt; 1,
      'default' =&gt; '',
      'visible_on_front' =&gt; 1,
      'source' =&gt; 'usuarios/entity_parent_id',
  ));
  
  if (version_compare(Mage::getVersion(), '1.4.2', '&gt;='))
  {
      Mage::getSingleton('eav/config')
      -&gt;getAttribute('customer', 'parent_id')
      -&gt;setData('used_in_forms', array('adminhtml_customer','customer_account_create','customer_account_edit','checkout_register','adminhtml_customer_address','customer_address_edit','customer_register_address'))
      -&gt;save();
      }
  </code></pre>
  
  <p>In Xkey/Usuarios/etc/config.xml</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;&lt;config&gt;
      &lt;modules&gt;
          &lt;Xkey_Usuarios&gt;
              &lt;version&gt;0.1.0&lt;/version&gt;
          &lt;/Xkey_Usuarios&gt;
      &lt;/modules&gt;
      &lt;global&gt;
          &lt;fieldsets&gt;
              &lt;customer_account&gt;
                  &lt;parent_id&gt;
                      &lt;create&gt;1&lt;/create&gt;
                      &lt;update&gt;1&lt;/update&gt;
                      &lt;name&gt;1&lt;/name&gt;
                  &lt;/parent_id&gt;
              &lt;/customer_account&gt;
          &lt;/fieldsets&gt;
          &lt;helpers&gt;
              &lt;usuarios&gt;
                  &lt;class&gt;Xkey_Usuarios_Helper&lt;/class&gt;
              &lt;/usuarios&gt;
          &lt;/helpers&gt;
          &lt;resources&gt;
              &lt;usuarios_setup&gt;
                  &lt;setup&gt;
                      &lt;module&gt;Xkey_Usuarios&lt;/module&gt;
                      &lt;class&gt;Mage_Customer_Model_Entity_Setup&lt;/class&gt;
                  &lt;/setup&gt;
                  &lt;connection&gt;
                      &lt;use&gt;core_setup&lt;/use&gt;
                  &lt;/connection&gt;
              &lt;/usuarios_setup&gt;
              &lt;usuarios_write&gt;
                  &lt;connection&gt;
                      &lt;use&gt;core_write&lt;/use&gt;
                  &lt;/connection&gt;
              &lt;/usuarios_write&gt;
              &lt;usuarios_read&gt;
                  &lt;connection&gt;
                      &lt;use&gt;core_read&lt;/use&gt;
                  &lt;/connection&gt;
              &lt;/usuarios_read&gt;
          &lt;/resources&gt;
          &lt;models&gt;
              &lt;sales&gt;
                  &lt;rewrite&gt;
                      &lt;order&gt;Xkey_Usuarios_Model_Order&lt;/order&gt;
                  &lt;/rewrite&gt;
              &lt;/sales&gt;
          &lt;/models&gt;   
      &lt;/global&gt;
  &lt;/config&gt;
  </code></pre>
  
  <p>In Xkey/Usuarios/Model/Entity/Parent_Id.php</p>
  
  <pre><code>&lt;?php 
      class Xkey_Usuarios_Model_Entity_Parent_Id extends Mage_Eav_Model_Entity_Attribute_Source_Abstract {
  
          public function getAllOptions() {
              if($this-&gt;_options === null) {
                  $this-&gt;_options = array();
                  $this-&gt;_options[] = array (
                      'value' =&gt; '1,',
                      'label' =&gt; 'Test 1'
                  );
              }
  
              return $this-&gt;_options;
          }
      }
  </code></pre>
  
  <p>I got this error: </p>
  
  <p>"Model-source" usuarios/entity_parent_id "not found for attribute" parent_id "" </p>
  
  <p>:/</p>