title: Shopify Product API (custom fields)
body: <p>I've been exploring the Shopify Products API, specifically the return of
  GET /admin/products.json</p>
  
  <p>And I can't find any return of custom fields in the Response that's provided in the documentation. Is this usually provided in the API and is nested in the JSON, or do you have to do a bit of relational digging to find the custom fields? Thanks in advance.</p>