title: Magento - Retrieve order products with a specific custom option
body: <p>I want to retrieve all product IDs that has a specific (custom) option value (provided by the customer in the frontend) from all orders - regardless of store/website.</p>
  
  <p>The option is a text field (<code>Mage_Catalog_Model_Product_Option_Type_Text</code>), the SKU (and title) is <strong>test_option</strong> and the value I'm looking for is <strong>green</strong>.</p>
  
  <p>I would prefer to do this with a raw MySQL query, but a solution using Magentos models/collections would definitely suffice.</p>