monolith-routing-and-middleware

# Monolith Routing and Middleware ## Use this skill when - Adding new HTTP endpoints. - Inserting request/response middleware. - Troubleshooting request flow issues. ## Routing fundamentals - Main router is `http.ServeMux` in `app/routes/routes.go`. - Routes are registered in `registerRoutes`. - Pattern format uses method + path (e.g., `"GET /widgets/{id}"`). ## Middleware fundamentals - Middleware registration order lives in `app/middleware/registration.go`. - Current baseline includes logging and CSRF middleware. - Middleware wraps mux globally through `InitServerHandler`. ## Adding middleware safely 1. Implement `func(http.Handler) http.Handler` in `app/middleware/`. 2. Add it to registration slice in desired order. 3. Ensure it is side-effect free and deterministic. 4. Add tests similar to existing middleware tests. ## CSRF behavior `CSRFMiddleware` leverages Go's cross-origin protections; keep it in the stack unless you intentionally disable protection for a specific reason.