Add Razorpay Webhook Support

[Prateek32177]

We want to add webhook support for Razorpay in tern. Razorpay sends events for payments, refunds, orders, and more via webhook integrations.

Tasks

Webhook Handler

• Implement /src/platforms/razorpay.ts.
• Normalize payloads into tern’s event format.

Platform Config

• Add platformConfigs.razorpay with supported events (e.g., payment.captured, payment.failed, order.paid, refund.processed).

Test Cases

• Add JSON fixtures for 3+ events (payment captured, order paid, refund processed).
• Write Jest tests in /tests/razorpay.test.ts.

Docs

• Update /docs/platforms.md with setup steps.
• Mention manual webhook verification steps. See Razorpay Webhook Verification Docs

Acceptance Criteria

• Razorpay handler implemented
• Manual webhook verification supported
• Tests with 3+ event types
• Docs updated

Helpful Links: Razorpay Webhooks Docs