title: Add checkbox to product inventory tab in WooCommerce and have the checkbox checked by default
body: <p>I got this snippet in <a href="https://stackoverflow.com/questions/54197716/how-i-set-a-checkbox-to-be-always-checked-in-woocommerce-product-admin">here</a>  to add checkbox custom field which is auto set and it’s working fine.</p>
  <pre class="lang-php prettyprint-override"><code>// Displaying quantity setting fields on admin product pages
  add_action( 'woocommerce_product_options_pricing', 'add_custom_field_product_options_pricing' );
  function add_custom_field_product_options_pricing() {
    global $product_object;
  
    echo '&lt;/div&gt;&lt;div class=&quot;options_group&quot;&gt;';
  
    $values = $product_object-&gt;get_meta('_cutom_meta_key');
  
     woocommerce_wp_checkbox( array( // Checkbox.
      'id'            =&gt; '_cutom_meta_key',
      'label'         =&gt; __( 'Custom label', 'woocommerce' ),
      'value'         =&gt; empty($values) ? 'yes' : $values,
      'description'   =&gt; __( 'Enable this to make something.', 'woocommerce' ),
     ) );
  }
  
  // Save quantity setting fields values
  add_action( 'woocommerce_admin_process_product_object', 'save_custom_field_product_options_pricing' );
  function save_custom_field_product_options_pricing( $product ) {
  $product-&gt;update_meta_data( '_cutom_meta_key', isset($_POST['_cutom_meta_key']) ? 'yes' : 'no');
  }
  </code></pre>
  <p><strong>My question:</strong> how to move this checkbox to be on the inventory tab and have the checkbox checked by default?</p>
  <p>I’ve tried changing :</p>
  <pre class="lang-php prettyprint-override"><code>add_action( 'woocommerce_product_options_pricing', 'add_custom_field_product_options_pricing' );
  </code></pre>
  <p>to:</p>
  <pre class="lang-php prettyprint-override"><code>add_action( 'woocommerce_product_options_inventory_product_data', 'add_custom_field_product_options_pricing' );
  </code></pre>
  <p>AND</p>
  <pre class="lang-php prettyprint-override"><code>add_action( 'woocommerce_admin_process_product_object', 'save_custom_field_product_options_pricing' );
  </code></pre>
  <p>to:</p>
  <pre class="lang-php prettyprint-override"><code>add_action( 'woocommerce_process_product_meta', 'save_custom_field_product_options_pricing' );
  </code></pre>
  <p>But to no avail. Any advice?</p>