Sylius Bosta Shipping Plugin

Bosta (Egypt) shipping for Sylius 2.1+:

• bosta shipping calculator: flat fee per channel, or Bosta's fee estimate for the customer's city with the flat fee as fallback. Configured on the shipping method (API key, pickup city, package size, COD payment methods...).
• Automatic delivery creation: at checkout for cash-on-delivery orders, when the order is paid for online payments. Runs after the response is sent, so checkout never waits on Bosta and a Bosta outage never breaks it.
• Same tracking number everywhere: the Sylius shipment tracking code is the Bosta tracking number.
• Webhooks on a static per-store URL keep the order in step: picked up / in transit → shipment shipped, delivered → cash-on-delivery payment completed → order fulfilled. Exceptions, returns, loss are shown to the merchant.
• Fault tolerant: every failure is stored with its reason; the admin can Retry, Recreate (cancels the pending Bosta delivery and creates a new one), Refresh status and print the Airway bill from the order page. Retries never create duplicates (stable uniqueBusinessReference; a lost response is recovered by reference).
• Bosta logo on the checkout shipping step; Bosta links on the admin order page (merchant view) and the customer order pages (public tracking).
• English and Arabic.