Add an field to select which Shipping Methods can be associated with PostNL and default to PostNL.
Steps to Test
Edit plugin settings from WooCommerce > Settings > Shipping > PostNL, Under "Checkout Settings" you will find "Shipping Methods" fill it with associated methods and save the settings.
After adding products to the cart, and selecting any associated method as a shipping method for the cart, PostNL fields should be displayed.
Also PostNL metabox should be displayed in the admin dashboard order edit screen.
Description
Add an field to select which Shipping Methods can be associated with PostNL and default to PostNL.
Steps to Test