Ready-Made Payment Gateway Platform

I need an already-built, production-ready payment gateway similar to Stripe or Checkout.com that I can license and deploy under my own branding. The solution must ship with:

• A secure web portal split into an admin dashboard (merchant onboarding, transaction monitoring, fee management) and a customer self-service area.
• Well-documented RESTful APIs and webhooks for seamless integration with websites, mobile apps, and third-party platforms.
• Built-in support for Credit/Debit Cards, Digital Wallets, and Bank Transfers out of the box.
• Email-and-password user authentication (if you offer OAuth or 2FA as optional add-ons, let me know).
• Full multi-currency processing so merchants can bill and settle in multiple currencies.
• Clear deployment instructions plus any SDKs, sample code, or Postman collections needed to test the endpoints.

If your system is already live with other clients, please share a demo URL or sandbox credentials so I can run a quick end-to-end test: create merchant → generate keys → process a test payment → view it in the admin panel.

I’m looking to move quickly, so highlight the tech stack, typical implementation timeline, and what level of post-handover support you provide (bug fixes, minor tweaks, documentation updates).