Now setting the discount code ID on orders before saving

[dparker1005]

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Changes proposed in this Pull Request:

Currently, discount codes are set for orders after the orders have been saved. This means that the discount code attributes are not correct during the pmpro_added_order hook and the pmpro_updated_order hook.

This PR updates the logic when saving orders at checkout and on the Edit Order page to set the discount code during the order save process to make sure that those actions work as expected.

Note: When using offiste gateways (such as Stripe Checkout or PayPal Express), the discount code will still not be available during the pmpro_added_order hook. This is because the order is initially added in token status and is later updated to success with the discount code added once the checkout is complete. In these cases, it is best to use the pmpro_after_checkout or pmpro_order_status_success hooks.

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Changelog entry

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[ideadude]

Looks good to ship.