| Mock-only endpoint for integration testing and development. Simulates creating a delivery request — mimics a real provider flow where KitchenHub initiates a delivery with a provider.

        Supports two modes:
        - **Custom delivery**: provide `delivery_data` with full delivery details.
        - **Template delivery**: provide `store_id`, `order_id` and `delivery_provider_id`
          — KitchenHub will generate the delivery from a template.

        The `delivery_order_id` from the response is used to simulate
        status updates via `PUT /v2/mock/deliveries/{delivery_order_id}/status/`.