ROOT CAUSE: The sanitize_payload() method was returning a whitelist of
allowed fields, but shipping_cost, shipping_title, custom_fields, and
customer_note were NOT included. This caused these values to be null
even though the frontend was sending them correctly.
Added:
- shipping_cost (float)
- shipping_title (sanitized text)
- custom_fields (array)
- customer_note (sanitized textarea)
This should fix shipping not being applied to order totals.
942fb48a0b