Hosted checkout

Every payment has a hosted checkout page at https://fastaar.com/pay/{reference} (returned as checkout_url when you create the payment). The page walks your customer through the payment in Bangla and English:

1. The customer picks a provider (bKash/Nagad) from your active MFS accounts.
2. They see your number, the exact amount, and step-by-step Send Money instructions.
3. After sending the money, they enter the TrxID from their confirmation SMS and the number they sent from.
4. The page polls while Fastaar matches the SMS forwarded by your paired phone — usually under a minute — then shows the result.

Integration tips

• Redirect to checkout_url right after creating the payment; the link is single-use and expires.
• Pass success_url and cancel_url to send the customer back to your site when they finish or cancel. Fastaar appends payment_id (and invoice_id, if set) to the URL.
• Pass your order reference as invoice_id — it is echoed back in the API response, webhooks, and the success redirect. Use metadata for any extra key/values.
• invoice_id is idempotent: retrying a create with the same invoice_id returns the existing payment (HTTP 200) instead of creating a duplicate, so a dropped connection never double-charges. Look one up later with GET https://fastaar.com/api/v1/payments?invoice_id=….
• Add per-account instructions (e.g. "Use reference: shop") under MFS Accounts — they appear on the page.
• The success redirect is for UX only — confirm orders from the payment.completed webhook, which is the source of truth.