Support WPML copy syncing for price updates from admin table

[NateWr]

When editing prices from the admin table, WPML does not sync the changes to post meta. They require a hook be added when the post meta is updated to sync these changes:

do_action( 'wpml_sync_custom_field', $id, 'fdm_item_price' );

This code shhould be added after the post meta update here: https://github.com/NateWr/food-and-drink-menu/blob/master/includes/class-custom-post-types.php#L941

More details can be found in the WPML forums here: https://wpml.org/forums/topic/why-does-wpml-not-listen-to-wp-api-functions-delete_post_meta-add_post_meta/#post-1500291

[strarsis]

@NateWr: Related solution: #46

[NateWr]

Can you describe in more detail how the code you posted in #46 addresses this problem?

[strarsis]

@NateWr: Yes, the wpml.xml is also used by Polylang and allows to define which fields should be copied over/synced instead independently translated. This is useful for e.g. the price field.

[NateWr]

I don't believe the wpml-config.xml file is sufficient to address this issue. This issue is specifically about the price editing feature that appears in the list of menu items. When saved, it updates the post meta (update_post_meta) without doing a full post save, and WPML does not hook into this function, regardless of the wpml-config.xml settings.