AIStudio SaaS Backend Development

I have already prototyped the front-end of my SaaS product in AIStudio and now need a production-ready backend that plugs in cleanly. Here is what I am after:

• Core services: full user management (registration, profile, roles), payment processing for subscriptions and one-off charges, plus an analytics & reporting layer so I can surface usage metrics to both admins and end-users.
• Data layer: a solid SQL database—please design the schema, create all migration scripts, and keep performance in mind for future scale.
• Security: OAuth is my preferred path for authentication and authorization. I’ll need the standard flows (sign-in, refresh, revocation) exposed through the API.
• API: clean REST (or GraphQL if you can justify the benefit) endpoints documented with Swagger/OpenAPI so my AIStudio front-end can consume them effortlessly.
• Payment gateway integration: connect to a mainstream provider and return webhooks I can act on.
• Analytics: aggregate key events and expose concise reporting endpoints; bonus points if you suggest lightweight dashboards or pre-calculated views.

Deliverables
1. Source code in a public-cloud friendly framework (Node.js, Python, Go—your call, as long as it is well-structured and tested).
2. Database schema and migrations.
3. Postman (or similar) collection demonstrating every endpoint.
4. Deployment guide covering environment variables, secrets handling, and CI/CD hooks.
5. Short hand-off call or video walkthrough so I can hit the ground running.

Acceptance criteria
• All endpoints authenticated via OAuth.
• Payments flow end-to-end in sandbox mode.
• At least three actionable analytics metrics exposed.
• Unit tests with 80 %+ coverage.

If this sounds like an engaging build and you have proven backend chops, I’d love to see how you’d approach it and an outline of the stack you recommend.