title: Sylius Standard 1.7 Fixtures: Where is the list of available options?
body: <p>How do you get the list of available options in sylius_fixtures.yaml? I can't find documentation of that anywhere. There must be a list somewhere: when I try to use an "illegal" parameter, there's an error message that lists all the available parameters for that particular node:</p>
  
  <pre><code>&gt; Unrecognized option "menu_taxon" under "channel.custom.my-channel".
  &gt; Available options are "account_verification_required", "
  &gt; base_currency", "code", "color", "contact_email", "currencies",
  &gt; "default_locale", "default_tax_zone", "enabled", "hostname", "lo
  &gt; cales", "name", "shop_billing_data", "skipping_payment_step_allowed",
  &gt; "skipping_shipping_step_allowed", "tax_calculation_strategy",
  &gt; "theme_name".
  </code></pre>
  
  <p>It would be more practical to have a complete list rather than generate an error on purpose every time.</p>